NFPA
®
110
Standard for
Emergency and Standby
Power Systems
2019
®
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ISBN: 978-145591996-3 (PDF)
ISBN: 978-145591997-0 (eBook)
®
ADDITIONAL IMPORTANT NOTICES AND DISCLAIMERS CONCERNING NFPA STANDARDS
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110-1
Copyright © 2018 National Fire Protection Association®. All Rights Reserved.
NFPA® 110
Standard for
Emergency and Standby Power Systems
2019 Edition
This edition of NFPA 110, Standard for Emergency and Standby Power Systems, was prepared by the
Technical Committee on Emergency Power Supplies and released by the Correlating Committee on
National Electrical Code®. It was acted on by NFPA at its June Association Technical Meeting held
June 11-14, 2018, in Las Vegas, NV. It was issued by the Standards Council on August 14, 2018, with
an effective date of September 3, 2018, and supersedes all previous editions.
This edition of NFPA 110 was approved as an American National Standard on September 3, 2018.
Origin and Development of NFPA 110
The Technical Committee on Emergency Power Supplies was organized in 1976 by NFPA in
recognition of the demand for viable guidelines for the assembly, installation, and performance of
electrical power systems used to supply critical and essential needs during outages of the primary
power source. The intent was to establish the equipment requirements necessary to achieve an onsite auxiliary electrical power source suitable to the needs of the applicable requirements and user
criteria.
In 1979, the committee’s report proposing adoption of NFPA 110 was published but withdrawn
because of issues involving the scope of the committee. In 1981, a revised report was returned to the
committee to resolve differences with other NFPA documents. At the 1982 NFPA Fall Meeting, the
committee’s report was adopted as a tentative standard (NFPA 110T-1983) to expose the document
to public review.
NFPA 110 was formally adopted as a standard at the 1984 NFPA Fall Meeting and designated as
the 1985 edition, which clarified scope statements, prototype testing, battery and bypass-isolation
switch requirements, and revised maintenance requirements.
The 1988 edition included several new definitions and further clarified transfer switch and
installation testing requirements.
The 1993 edition reflected the adoption of NFPA 111, Standard on Stored Electrical Energy Emergency
and Standby Power Systems, a basic requirement for one-step loading for all prime movers, an update
on battery technology, restrictions on unnecessary transferring of loads, and the need for battery
maintenance.
The 1996 edition added revised monthly load testing requirements for generator sets,
consideration for potential wet stacking, various types of fuel tanks and spillage considerations,
restrictions on the types of permitted batteries, and working space requirements. It also clarified the
minimum number of cranks that an engine must be capable of completing, cooling system
requirements, and timing devices in health care facilities for testing a generator.
The 1999 edition deleted the testing of generator sets at 50 percent of the emergency power
supply system load because the relevant measure is the nameplate rating. The exception for wet
stacking was also deleted. Exhaust temperature monitoring was added because it is an acceptable
performance measure of proper emergency power supply loading.
The 2002 edition was restructured to comply with the Manual of Style for NFPA Technical Committee
Documents. Introductory material in Chapter 1 was formatted for consistency among all NFPA
documents. Referenced publications were relocated from the last chapter to Chapter 2, resulting in
the renumbering of chapters. Definitions in Chapter 3 were made consistent with definitions in
other NFPA documents, systematically aligned, and individually numbered. Paragraphs were revised
to provide one mandatory requirement per section, subsection, or paragraph. Information that
NFPA and National Fire Protection Association are registered trademarks of the National Fire Protection Association, Quincy, Massachusetts 02169.
110-2
EMERGENCY AND STANDBY POWER SYSTEMS
accompanied many of the requirements was moved to Annex A, Explanatory Material. Many exceptions were deleted or
rephrased into mandatory text.
Changes in the 2002 edition included definitive and broad-based requirements regarding electrical installations in
accordance with NFPA 70®, National Electrical Code®; additional EPS controls and safeguards, such as alerting staff of impending
failure of the EPS to start; access and working space around the generator set; ventilation; energy converters; and EPSS testing
requirements.
The 2005 edition revised clearance distances between transfer switches and service equipment, revised the definitions for
both lead-acid (flooded) and valve-regulated lead-acid (VRLA) batteries, and changed the testing and maintenance section to
include testing for spark-ignited engines that parallels those for diesel. Changes also included new annex material for diesel
fuel testing and maintenance procedures, as well as transfer switches.
Significant revisions to the 2010 edition included the following:
(1) Clarified that the requirements to systems classed as optional standby is not mandatory
(2) Clarified that the operation testing and routine maintenance requirements of Chapter 8 cover both new and existing
EPSSs
(3) Aligned the definitions of transfer switch types with NFPA 111 and relevant product standards
(4) Revised the Chapter 7 requirements for acceptance testing and differentiated what is required for new and
unoccupied buildings and facilities from what is required for existing occupied buildings and facilities
(5) Revised the Chapter 8 requirements for operational test durations, loading conditions, and method of test initiation
for the emergency power supply
A noteworthy change for the 2013 edition was the deletion of the mandatory 96-hour fuel supply requirement (5.1.2) for
seismic categories. The need for continued operation and the minimum operational time without refueling is a design
consideration or is directed by another standard. Several references to ASTM standards and additional annex material were
added to address fuel quality and storage issues. The prime mover cooling and ventilation system construction and installation
requirements were reorganized.
The 2016 edition was revised to prohibit the installation of an automatically actuated valve into the fuel lines to prevent the
inadvertent cutoff of fuel at critical times. The proper operation of systems connected in parallel was addressed by adding
acceptance testing and maintenance items for paralleling gear. To test all transfer switches, a requirement to rotate the transfer
switch initiating the monthly test was added where multiple transfer switches are installed. A new section was added to
consolidate record management and define record retention requirements.
For the 2019 edition, several existing requirements have been clarified to assist users with the proper application.
Clarifications include the location and access to the remote emergency stop switch, testing of fuel in accordance with the
manufacturer’s recommendations in lieu of an ASTM standard, and battery charger specifications.
2019 Edition
COMMITTEE PERSONNEL
110-3
Correlating Committee on National Electrical Code®
Michael J. Johnston, Chair
National Electrical Contractors Association, MD [IM]
Mark W. Earley, Secretary
National Fire Protection Association, MA
James E. Brunssen, Telcordia Technologies (Ericsson), NJ [UT]
Rep. Alliance for Telecommunications Industry Solutions
Kevin L. Dressman, U.S. Department of Energy, MD [U]
Palmer L. Hickman, Electrical Training Alliance, MD [L]
Rep. International Brotherhood of Electrical Workers
David L. Hittinger, Independent Electrical Contractors of Greater
Cincinnati, OH [IM]
Rep. Independent Electrical Contractors, Inc.
Richard A. Holub, The DuPont Company, Inc., DE [U]
Rep. American Chemistry Council
John R. Kovacik, UL LLC, IL [RT]
Alan Manche, Schneider Electric, KY [M]
Roger D. McDaniel, Georgia Power Company, GA [UT]
Rep. Electric Light & Power Group/EEI
James F. Pierce, Intertek Testing Services, OR [RT]
Vincent J. Saporita, Eaton’s Bussmann Business, MO [M]
Rep. National Electrical Manufacturers Association
David A. Williams, Delta Charter Township, MI [E]
Rep. International Association of Electrical Inspectors
Alternates
Lawrence S. Ayer, Biz Com Electric, Inc., OH [IM]
(Alt. to David L. Hittinger)
Roland E. Deike, Jr., CenterPoint Energy, Inc., TX [UT]
(Alt. to Roger D. McDaniel)
James T. Dollard, Jr., IBEW Local Union 98, PA [L]
(Alt. to Palmer L. Hickman)
Ernest J. Gallo, Telcordia Technologies (Ericsson), NJ [UT]
(Alt. to James E. Brunssen)
Robert A. McCullough, Tuckerton, NJ [E]
(Alt. to David A. Williams)
Robert D. Osborne, UL LLC, NC [RT]
(Alt. to John R. Kovacik)
Christine T. Porter, Intertek Testing Services, WA [RT]
(Alt. to James F. Pierce)
George A. Straniero, AFC Cable Systems, Inc., NJ [M]
(Alt. to Vincent J. Saporita)
Nonvoting
Timothy J. Pope, Canadian Standards Association, Canada [SE]
Rep. CSA/Canadian Electrical Code Committee
William R. Drake, Fairfield, CA [M]
(Member Emeritus)
D. Harold Ware, Libra Electric Company, OK [IM]
(Member Emeritus)
Mark W. Earley, NFPA Staff Liaison
This list represents the membership at the time the Committee was balloted on the final text of this edition.
Since that time, changes in the membership may have occurred. A key to classifications is found at the
back of the document.
NOTE: Membership on a committee shall not in and of itself constitute an endorsement of
the Association or any document developed by the committee on which the member serves.
Committee Scope: This Committee shall have primary responsibility for documents on
minimizing the risk of electricity as a source of electric shock and as a potential ignition
source of fires and explosions. It shall also be responsible for text to minimize the
propagation of fire and explosions due to electrical installations.
2019 Edition
110-4
EMERGENCY AND STANDBY POWER SYSTEMS
Technical Committee on Emergency Power Supplies
Dan Chisholm, Sr., Chair
MGI Systems, Inc., FL [IM]
Ernest E. Allen, The Doctors Company, OH [I]
Rep. NFPA Health Care Section
Kenneth A. Cotton, U.S. Energy/Donlee Crop, CA [M]
Jason D’Antona, Thompson Consultants, Inc., MA [SE]
David A. Dagenais, Partners/Wentworth-Douglass Hospital, NH [U]
Richard L. Day, Michigan State Fire Marshal’s Office, MI [E]
Dennis DeMoss, Sargent & Lundy, IL [SE]
Louis J. Feller, U.S. Army Corps of Engineers, WA [U]
James R. (Skip) Gregory, Health Facility Consulting, FL [E]
Rep. Florida Agency for Health Care Administration
Ross M. Hardy, The University of Michigan Medical Center, MI [U]
Jonathan Hartsell, Rodgers, NC [IM]
Oleh Kowalskyj, U.S. Department of Veterans Affairs, DC [U]
Rep. U.S. Department of Veterans Affairs
Pouyan Layegh, University of Texas MD Anderson Cancer Center,
TX [U]
Chad E. Loomis, Cornell University, NY [U]
Alan Manche, Schneider Electric, KY [M]
Dermott Murphy, Washington State Patrol - Fire Prevention Bureau,
WA [E]
Hugh O. Nash, Jr., Nash-Consult, TN [SE]
Daniel J. O’Connor, JENSEN HUGHES, IL [SE]
Gary L. Olson, kW Rx, LLC, MN [SE]
Steve R. Sappington, Caterpillar Inc., GA [M]
Ronald A. Schroeder, ASCO Power Technologies, LP, NJ [M]
Randy H. Schubert, Ericsson, NJ [U]
Rep. Alliance for Telecommunications Industry Solutions
Ronald M. Smidt, Carolinas HealthCare System, NC [U]
Rep. American Society for Healthcare Engineering
Raymond J. Stanko, UL LLC, IL [RT]
David Stymiest, Smith Seckman Reid, Inc., TN [SE]
Herbert V. Whittall, Electrical Generating Systems Association, FL
[M]
Timothy P. Windey, Cummins Power Generation, MN [M]
Stephen Works, Blanchard Machinery, SC [IM]
Alternates
Raymond J. Battalora, JENSEN HUGHES, TX [SE]
(Alt. to Daniel J. O’Connor)
Dan Chisholm, Jr., MGI Systems, Inc., FL [IM]
(Alt. to Dan Chisholm, Sr.)
Joshua Dugger, Facility Shield International, CA [M]
(Alt. to Kenneth A. Cotton)
Brian J. Escott, ASCO Power Technologies, NJ [M]
(Alt. to Ronald A. Schroeder)
James Hunt, Hostrat Inc., WA [M]
(Alt. to Herbert V. Whittall)
Richard G. Kluge, Ericsson, NJ [U]
(Alt. to Randy H. Schubert)
Gary Krauch, Virginia New England Healthcare System, MA [U]
(Alt. to Oleh Kowalskyj)
Michael J. Lang, Mersen, GA [M]
(Voting Alt.)
Rich Scroggins, Cummins Power Generation, MN [M]
(Voting Alt.)
David C. Skiba, Sargent & Lundy LLC, IL [SE]
(Alt. to Dennis DeMoss)
Bogue M. Waller, Gresham Smith & Partners, TN [SE]
(Alt. to Hugh O. Nash, Jr.)
Nonvoting
William H. Everard, Everard Mid Atlantic Inc., VA [SE]
(Member Emeritus)
Christopher Coache, NFPA Staff Liaison
This list represents the membership at the time the Committee was balloted on the final text of this edition.
Since that time, changes in the membership may have occurred. A key to classifications is found at the
back of the document.
NOTE: Membership on a committee shall not in and of itself constitute an endorsement of
the Association or any document developed by the committee on which the member serves.
Committee Scope: This Committee shall have primary responsibility for documents on
performance criteria for the selection and assembly of the components for emergency and
standby power systems in buildings and facilities, including categories of power supplies,
transfer equipment, controls, supervisory equipment, and all related electrical and
mechanical auxiliary or accessory equipment needed to supply emergency or standby power
to the utilization equipment. The Committee also shall be responsible for criteria on the
maintenance and testing of the system. This Committee does not cover requirements for the
application of emergency power systems, self-contained emergency lighting units, and
electrical wiring, except that wiring that is an integral part of the system up to the load side
of the transfer switch(es). This Committee shall report to Correlating Committee of the
National Electrical Code®.
2019 Edition
CONTENTS
110-5
Contents
Chapter
1.1
1.2
1.3
1.4
1
Administration ............................................
Scope. ...................................................................
Purpose. ...............................................................
Application. ..........................................................
Equivalency. .........................................................
110– 6
110– 6
110– 6
110– 6
110– 6
Chapter
2.1
2.2
2.3
2.4
2
Referenced Publications ............................
General. ................................................................
NFPA Publications. ..............................................
Other Publications. .............................................
References for Extracts in Mandatory Sections.
110– 6
110– 6
110– 6
110– 7
110– 7
Chapter
3.1
3.2
3.3
3
Definitions ...................................................
General. ................................................................
NFPA Official Definitions. ..................................
General Definitions. ............................................
110– 7
110– 7
110– 7
110– 7
Chapter 4
4.1
4.2
4.3
4.4
Classification of Emergency Power Supply
Systems (EPSSs) ..........................................
General. ................................................................
Class. .....................................................................
Type. .....................................................................
Level. ....................................................................
110– 8
110– 8
110– 8
110– 8
110– 8
Chapter 5
Emergency Power Supply (EPS): Energy
Sources, Converters, and Accessories .......
Energy Sources. ...................................................
Energy Converters — General. ...........................
Energy Converters — Temperature
Maintenance. .......................................................
Energy Converters — Capacity. ..........................
Energy Converters — Fuel Supply. .....................
Rotating Equipment. ...........................................
110– 9
110– 9
110– 9
110– 9
Chapter 6
Transfer Switch Equipment ........................
6.1
General. ................................................................
110– 14
110– 14
5.1
5.2
5.3
5.4
5.5
5.6
110– 8
110– 8
110– 8
6.2
6.3
6.4
6.5
ATS Features. .......................................................
Requirements for Paralleled Generator Sets. ....
Bypass-Isolation Switches. ...................................
Protection. ...........................................................
Chapter 7
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
7.10
7.11
7.12
7.13
Installation and Environmental
Considerations ............................................
General. ................................................................
Location. ..............................................................
Lighting. ...............................................................
Mounting. ............................................................
Vibration. .............................................................
Noise. ....................................................................
Heating, Cooling, and Ventilating. ....................
Installed EPS Cooling System. ............................
Fuel System. .........................................................
Exhaust System. ...................................................
Protection. ...........................................................
Distribution. .........................................................
Installation Acceptance. ......................................
110– 14
110– 15
110– 15
110– 15
110– 15
110– 15
110– 16
110– 16
110– 16
110– 16
110– 16
110– 16
110– 17
110– 17
110– 18
110– 18
110– 18
110– 19
Chapter 8
Routine Maintenance and Operational
Testing .........................................................
General. ................................................................
Manuals, Special Tools, and Spare Parts. ...........
Maintenance and Operational Testing. .............
Operational Inspection and Testing. .................
Records. ................................................................
110– 20
110– 20
110– 20
110– 20
110– 20
110– 21
Annex A
Explanatory Material ..................................
110– 22
Annex B
Diagrams of Typical Systems ......................
110– 35
Annex C
Informational References ..........................
110– 39
Index
.....................................................................
110– 41
8.1
8.2
8.3
8.4
8.5
2019 Edition
110-6
EMERGENCY AND STANDBY POWER SYSTEMS
NFPA 110
Standard for
Emergency and Standby Power Systems
2019 Edition
IMPORTANT NOTE: This NFPA document is made available for
use subject to important notices and legal disclaimers. These notices
and disclaimers appear in all publications containing this document
and may be found under the heading “Important Notices and
Disclaimers Concerning NFPA Standards.” They can also be viewed
at www.nfpa.org/disclaimers or obtained on request from NFPA.
UPDATES, ALERTS, AND FUTURE EDITIONS: New editions of
NFPA codes, standards, recommended practices, and guides (i.e.,
NFPA Standards) are released on scheduled revision cycles. This
edition may be superseded by a later one, or it may be amended
outside of its scheduled revision cycle through the issuance of Tenta‐
tive Interim Amendments (TIAs). An official NFPA Standard at any
point in time consists of the current edition of the document, together
with all TIAs and Errata in effect. To verify that this document is the
current edition or to determine if it has been amended by TIAs or
Errata, please consult the National Fire Codes® Subscription Service
or the “List of NFPA Codes & Standards” at www.nfpa.org/docinfo.
In addition to TIAs and Errata, the document information pages also
include the option to sign up for alerts for individual documents and
to be involved in the development of the next edition.
NOTICE: An asterisk (*) following the number or letter
designating a paragraph indicates that explanatory material on
the paragraph can be found in Annex A.
A reference in brackets [ ] following a section or paragraph
indicates material that has been extracted from another NFPA
document. As an aid to the user, the complete title and edition
of the source documents for extracts in mandatory sections of
the document are given in Chapter 2 and those for extracts in
informational sections are given in Annex C. Extracted text
may be edited for consistency and style and may include the
revision of internal paragraph references and other references
as appropriate. Requests for interpretations or revisions of
extracted text shall be sent to the technical committee respon‐
sible for the source document.
Information on referenced publications can be found in
Chapter 2 and Annex C.
Chapter 1 Administration
1.1 Scope. This standard contains requirements covering the
performance of emergency and standby power systems provid‐
ing an alternate source of electrical power to loads in buildings
and facilities in the event that the primary power source fails.
1.1.1 Power systems covered in this standard include power
sources, transfer equipment, controls, supervisory equipment,
and all related electrical and mechanical auxiliary and acces‐
sory equipment needed to supply electrical power to the load
terminals of the transfer equipment.
1.1.2 This standard covers installation, maintenance, opera‐
tion, and testing requirements as they pertain to the perform‐
ance of the emergency power supply system (EPSS).
1.1.3 This standard does not cover the following:
(1)
Application of the EPSS
2019 Edition
(2)
(3)
(4)
(5)
(6)
Emergency lighting unit equipment
Distribution wiring
Utility service when such service is permitted as the EPSS
Parameters for stored energy devices
The equipment of systems that are not classed as Level 1
or Level 2 systems in accordance with Chapter 4 of this
standard
1.1.4* This standard does not establish criteria for stored
energy systems.
1.1.5 The selection of any of the following is not within the
scope of this standard:
(1) Specific buildings or facilities, or both, requiring an EPSS
(2) Specific loads to be served by the EPSS
(3)* Assignment of type, class, or level to any specific load
1.2 Purpose. This standard contains performance require‐
ments for an EPSS.
1.2.1 It is the role of other NFPA standards to specify which
occupancies require an EPSS and the applicable level, type,
and class. This standard does not specify where an EPSS is
required.
1.2.2 This standard also is intended to provide guidance for
inspectors, designers, installers, manufacturers, and users of
EPSSs and to serve as a vehicle for communication between the
parties involved. It is not intended as a design manual.
1.2.3 Compliance with this standard is not intended to
exempt the parties involved from their respective responsibili‐
ties for the design, installation, maintenance, performance, or
compliance with other applicable standards and codes.
1.3 Application. This document applies to new installations of
EPSSs, except that the requirements of Chapter 8 shall apply to
new and existing systems. Existing systems shall not be required
to be modified to conform, except where the authority having
jurisdiction determines that nonconformity presents a distinct
hazard to life.
1.4 Equivalency. Nothing in this standard is intended to
prevent the use of systems, methods, or devices of equivalent or
superior quality, strength, fire resistance, effectiveness, durabil‐
ity, and safety to those prescribed by this standard.
1.4.1* Technical documentation shall be submitted to the
authority having jurisdiction to demonstrate equivalency.
1.4.2 The system, method, or device shall be approved for the
intended purpose by the authority having jurisdiction.
Chapter 2 Referenced Publications
2.1 General. The documents or portions thereof listed in this
chapter are referenced within this standard and shall be
considered part of the requirements of this document.
2.2 NFPA Publications. National Fire Protection Association,
1 Batterymarch Park, Quincy, MA 02169-7471.
NFPA 30, Flammable and Combustible Liquids Code, 2018
edition.
NFPA 37, Standard for the Installation and Use of Stationary
Combustion Engines and Gas Turbines, 2018 edition.
NFPA 54, National Fuel Gas Code, 2018 edition.
NFPA 58, Liquefied Petroleum Gas Code, 2017 edition.
DEFINITIONS
NFPA 70®, National Electrical Code®, 2017 edition.
NFPA 72®, National Fire Alarm and Signaling Code®, 2016
edition.
NFPA 99, Health Care Facilities Code, 2018 edition.
NFPA 780, Standard for the Installation of Lightning Protection
Systems, 2017 edition.
2.3 Other Publications.
2.3.1 ASCE Publications. American Society of Civil Engineers,
1801 Alexander Bell Drive, Reston, VA 20191.
ASCE/SEI 7, Minimum Design Loads for Buildings and Other
Structures, 2010.
2.3.2 Other Publications.
Merriam-Webster’s Collegiate Dictionary, 11th edition, MerriamWebster, Inc., Springfield, MA, 2003.
2.4 References for Extracts in Mandatory Sections.
NFPA 1, Fire Code, 2018 edition.
NFPA 70®, National Electrical Code®, 2017 edition.
NFPA 790, Standard for Competency of Third-Party Field Evalua‐
tion Bodies, 2018 edition.
110-7
3.2.6 Should. Indicates a recommendation or that which is
advised but not required.
3.2.7 Standard. An NFPA Standard, the main text of which
contains only mandatory provisions using the word “shall” to
indicate requirements and that is in a form generally suitable
for mandatory reference by another standard or code or for
adoption into law. Nonmandatory provisions are not to be
considered a part of the requirements of a standard and shall
be located in an appendix, annex, footnote, informational
note, or other means as permitted in the NFPA Manuals of
Style. When used in a generic sense, such as in the phrase
“standards development process” or “standards development
activities,” the term “standards” includes all NFPA Standards,
including Codes, Standards, Recommended Practices, and
Guides.
3.3 General Definitions.
3.3.1* Battery Certification. The certification by a battery
manufacturer that a battery is built to industry standards.
3.3.2 Black Start. Where the stored energy system has the
capability to start the prime mover without using energy from
another source.
Chapter 3 Definitions
3.3.3* Emergency Power Supply (EPS). The source of electric
power of the required capacity and quality for an emergency
power supply system (EPSS).
3.1 General. The definitions contained in this chapter shall
apply to the terms used in this standard. Where terms are not
defined in this chapter or within another chapter, they shall be
defined using their ordinarily accepted meanings within the
context in which they are used. Merriam-Webster’s Collegiate
Dictionary, 11th edition, shall be the source for the ordinarily
accepted meaning.
3.3.4* Emergency Power Supply System (EPSS). A complete
functioning EPS system coupled to a system of conductors,
disconnecting means and overcurrent protective devices, trans‐
fer switches, and all control, supervisory, and support devices
up to and including the load terminals of the transfer equip‐
ment needed for the system to operate as a safe and reliable
source of electric power.
3.2 NFPA Official Definitions.
3.3.5 Field Evaluation Body (FEB). An organization, or part
of an organization, that performs field evaluations of electrical
or other equipment. [790, 2018]
3.2.1* Approved. Acceptable to the authority having jurisdic‐
tion.
3.2.2* Authority Having Jurisdiction (AHJ). An organization,
office, or individual responsible for enforcing the requirements
of a code or standard, or for approving equipment, materials,
an installation, or a procedure.
3.2.3 Labeled. Equipment or materials to which has been
attached a label, symbol, or other identifying mark of an organ‐
ization that is acceptable to the authority having jurisdiction
and concerned with product evaluation, that maintains peri‐
odic inspection of production of labeled equipment or materi‐
als, and by whose labeling the manufacturer indicates
compliance with appropriate standards or performance in a
specified manner.
3.2.4* Listed. Equipment, materials, or services included in a
list published by an organization that is acceptable to the
authority having jurisdiction and concerned with evaluation of
products or services, that maintains periodic inspection of
production of listed equipment or materials or periodic evalua‐
tion of services, and whose listing states that either the equip‐
ment, material, or service meets appropriate designated
standards or has been tested and found suitable for a specified
purpose.
3.2.5 Shall. Indicates a mandatory requirement.
3.3.6 Field Labeled (as applied to evaluated products). Equip‐
ment or materials to which has been attached a label, symbol,
or other identifying mark of an FEB indicating the equipment
or materials were evaluated and found to comply with require‐
ments as described in an accompanying field evaluation report.
[70:100]
3.3.7 Fuel Tank.
3.3.7.1 Day Fuel Tank. A fuel tank, located inside a struc‐
ture, that provides fuel to the engine.
3.3.7.2 Enclosed Fuel Tank. A fuel tank located within a
separate room, separated from other equipment.
3.3.7.3 Integral Fuel Tank in EPS Systems. A fuel tank
furnished by the EPS supplier and mounted on the engine
or under as a subbase.
3.3.7.4 Main Fuel Tank. A separate, main fuel tank for
supplying fuel to the engine or a day tank.
3.3.8 Lamp. An illuminating indicator.
3.3.9 Lead-Acid Battery.
3.3.9.1* Valve-Regulated (VRLA). A lead-acid battery consist‐
ing of sealed cells furnished with a valve that opens to vent
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110-8
EMERGENCY AND STANDBY POWER SYSTEMS
the battery whenever the internal pressure of the battery
exceeds the ambient pressure by a set amount. [1, 2018]
3.3.9.2* Vented (Flooded). A lead-acid battery consisting of
cells that have electrodes immersed in liquid electrolyte.
3.3.10 Occupancy Category. See ASCE/SEI 7, Minimum
Design Loads for Buildings and Other Structures.
3.3.11 Qualified Person. One who has skills and knowledge
related to the operation, maintenance, repair, and testing of
the EPSS equipment and installations and has received safety
training to recognize and avoid the hazards involved.
3.3.12 Switch.
3.3.12.1 Automatic Transfer Switch (ATS). Self-acting equip‐
ment for transferring the connected load from one power
source to another power source.
3.3.12.2 Bypass-Isolation Switch. A manually operated
device used in conjunction with an automatic transfer switch
to provide a means of directly connecting load conductors
to a power source and disconnecting the automatic transfer
switch.
3.3.12.3 Nonautomatic Transfer Switch. A device, operated
manually by a physical action or electrically by either a local
or remote control, for transferring a common load between
a normal and alternate supply.
Chapter 4 Classification of Emergency Power Supply Systems
(EPSSs)
4.1* General. The EPSS shall provide a source of electrical
power of required capacity, reliability, and quality to loads for a
length of time as specified in Table 4.1(a) and within a speci‐
fied time following loss or failure of the normal power supply
as specified in Table 4.1(b).
4.2* Class. The class defines the minimum time, in hours, for
which the EPSS is designed to operate at its rated load without
being refueled or recharged. [See Table 4.1(a).]
Table 4.1(a) Classification of EPSSs
Class
Minimum Time
Class 0.083
Class 0.25
Class 2
Class 6
Class 48
Class X
0.083 hr (5 min)
0.25 hr (15 min)
2 hr
6 hr
48 hr
Other time, in hours, as required by the
application, code, or user
Table 4.1(b) Types of EPSSs
Designation
Power Restoration
Type U
Type 10
Type 60
Type 120
Type M
Basically uninterruptible (UPS systems)
10 sec
60 sec
120 sec
Manual stationary or nonautomatic — no
time limit
2019 Edition
4.3 Type. The type defines the maximum time, in seconds,
that the EPSS will permit the load terminals of the transfer
switch to be without acceptable electrical power. Table 4.1(b)
provides the types defined by this standard.
4.4* Level. This standard recognizes two levels for equipment
installation, performance, and maintenance requirements.
4.4.1* Level 1 systems shall be installed where failure of the
equipment to perform could result in loss of human life or seri‐
ous injuries.
4.4.2* Level 2 systems shall be installed where failure of the
EPSS to perform is less critical to human life and safety.
4.4.3* All equipment shall be permanently installed.
4.4.4* Level 1 and Level 2 systems shall ensure that all loads
served by the EPSS are supplied with alternate power that
meets all the following criteria:
(1)
(2)
(3)
Of a quality within the operating limits of the load
For a duration specified for the class as defined in Table
4.1(a)
Within the time specified for the type as defined in Table
4.1(b)
Chapter 5 Emergency Power Supply (EPS): Energy Sources,
Converters, and Accessories
5.1 Energy Sources.
5.1.1* The following energy sources shall be permitted to be
used for the emergency power supply (EPS):
(1)* Liquid petroleum products at atmospheric pressure
specified in the appropriate ASTM standards and
recommended by the engine manufacturer
(2)* Liquefied petroleum gas (liquid or vapor withdrawal)
specified in the appropriate ASTM standards and
recommended by the engine manufacturer
(3)* Natural or synthetic gas
as
as
as
as
Exception: For Level 1 installations in locations where the probability of
interruption of off-site fuel supplies is high, on-site storage of an alter‐
nate energy source sufficient to allow full output of the EPSS to be deliv‐
ered for the class specified shall be required, with the provision for
automatic transfer from the primary energy source to the alternate
energy source.
5.1.2 The energy sources listed in 5.1.1 shall be permitted to
be used for the EPS where the primary source of power is by
means of on-site energy conversion, provided that there is sepa‐
rately dedicated energy conversion equipment on-site with a
capacity equal to the power needs of the EPSS.
5.1.3* A public electric utility that has a demonstrated reliabil‐
ity shall be permitted to be used as the EPS where the primary
source is by means of on-site energy conversion.
5.2 Energy Converters — General.
5.2.1 Energy converters shall consist only of rotating equip‐
ment as indicated in 5.2.4.
5.2.1.1 Level 1 energy converters shall be representative prod‐
ucts built from components that have proven compatibility and
reliability and are coordinated to operate as a unit.
EMERGENCY POWER SUPPLY (EPS): ENERGY SOURCES, CONVERTERS, AND ACCESSORIES
110-9
5.2.1.2 The capability of the energy converter, with its controls
and accessories, to survive without damage from common and
abnormal disturbances in actual load circuits shall be demon‐
strable by tests on separate prototype models, or by acceptable
tests on the system components as performed by the compo‐
nent suppliers, or by tests performed in the listing process for
the assembly.
5.3.2 All prime mover heaters shall be automatically deactiva‐
ted while the prime mover is running. (For combustion turbines,
see 5.3.5.)
5.2.1.3 A separate prototype unit shall be permitted to be
utilized in a Level 1 or Level 2 installation, provided that all
prototype tests produce no deleterious effects on the unit, and
the authority having jurisdiction, the owner, and the user are
informed that the unit is the prototype test unit.
5.3.3 Antifreeze protection shall be provided according to the
manufacturer's recommendations.
5.2.2* The rotating equipment prototype unit shall be tested
with all typical prime mover accessories that affect its power
output in place and operating, including, but not limited to,
the following:
(1)
(2)
(3)
(4)
(5)
(6)
Battery-charging alternator
Water pump
Radiator fan for unit-mounted radiators or oil coolers (or
comparable load)
Fuel pump and fuel filter(s)
Air filter(s)
Exhaust mufflers or restriction simulating the maximum
backpressure recommended by the prime mover manu‐
facturer
5.2.3 The energy converter for Level 1 systems shall be specifi‐
cally designed, assembled, and tested to ensure system opera‐
tion under the following conditions:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
Short circuits
Load surges due to motor starting
Elevator operations
Silicon controlled rectifier (SCR) controllers
X-ray equipment
Overspeed, overtemperature, or overload
Adverse environmental conditions
5.2.4 Rotating equipment shall consist of a generator driven
by one of the following prime mover types:
(1)
(2)
(3)
Otto cycle (spark ignited)
Diesel cycle
Gas turbine cycle
5.2.4.1 Other types of prime movers and their associated
equipment meeting the applicable performance requirements
of this standard shall be permitted, if acceptable to the author‐
ity having jurisdiction.
5.2.4.2 Where used for Level 1 applications, the prime mover
shall not mechanically drive any equipment other than its oper‐
ating accessories and its generator.
5.2.5 The EPS shall be installed in accordance with NFPA 70.
Exception: When a listing process is not available for the enginegenerator assembly, a field evaluation body acceptable to the authority
having jurisdiction shall be permitted to affix a field label.
5.3.2.1 Air-cooled prime movers shall be permitted to employ
a heater to maintain lubricating oil temperature as recommen‐
ded by the prime mover manufacturer.
5.3.4 Ether-type starting aids shall not be permitted.
5.3.5 The ambient air temperature in the EPS equipment
room or outdoor housing containing Level I rotating equip‐
ment shall stabilize at not less than 4.5°C (40°F) when the
equipment is not operating.
5.4* Energy Converters — Capacity. The energy converters
shall have the required capacity and response to pick up and
carry the load within the time specified in Table 4.1(b) after
loss of primary power.
5.5 Energy Converters — Fuel Supply.
5.5.1 The fuel supplies specified in 5.1.1(1) and 5.1.1(2) for
energy converters intended for Level 1 use shall not be used
for any other purpose. (For fuel system requirements, see
Section 7.9.)
5.5.1.1 Enclosed fuel tanks shall be permitted to be used for
supplying fuel for other equipment, provided that the draw‐
down level or other passive features are designed into the fuel
system to guarantee that the required quantity of fuel is availa‐
ble for the EPSS.
5.5.1.2 Vapor-withdrawal LP-Gas systems shall have a dedica‐
ted fuel supply.
5.5.2* A low-fuel sensing switch shall be provided for the main
fuel supply tank(s) using the energy sources listed in 5.1.1(1)
and 5.1.1(2) to indicate when less than the minimum fuel
necessary for full load running, as required by the specified
class in Table 4.1(a), remains in the main fuel tank.
5.5.3* The main fuel tank shall have a minimum capacity of at
least 133 percent of either the low-fuel sensor quantity speci‐
fied in 5.5.2 or the quantity required to support the duration of
run specified in Table 4.1(a).
5.6 Rotating Equipment.
5.6.1 General. Prime movers and accessories shall comply
with NFPA 37 except as modified in this standard.
5.6.2 Prime Mover Ratings. Proper derating factors, such as
altitudes, ambient temperature, fuel energy content, accessory
losses, and site conditions as recommended by the manufac‐
turer of the engine shall be used in determining whether or
not brake power meets the connected load requirements.
5.3 Energy Converters — Temperature Maintenance.
5.3.1 The EPS shall be heated as necessary to maintain the
water jacket and battery temperature determined by the EPS
manufacturer for cold start and load acceptance for the type of
EPSS.
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EMERGENCY AND STANDBY POWER SYSTEMS
5.6.3 Prime Mover Accessories.
5.6.3.1 Governors shall maintain a bandwidth of rated
frequency for any constant load (steady-state condition) that is
compatible with the load.
5.6.3.1.1 The frequency droop between no load and full load
shall be within the range for the load.
5.6.3.1.2 The frequency dip upon one-step application of the
full load shall not be outside the range for the load, with a
return to steady-state conditions occurring within the require‐
ments of the load.
5.6.4.1.1 Electric starter systems shall start using a positive
shift solenoid to engage the starter motor and to crank the
prime mover for the period specified in 5.6.4.2 without over‐
heating, at a speed at least equal to that recommended by the
manufacturer of the prime mover and at the lowest ambient
temperature anticipated at the installation site.
5.6.4.1.2 Other types of stored energy starting systems (except
pyrotechnic) shall be permitted to be used where recommen‐
ded by the manufacturer of the prime mover and subject to
approval of the authority having jurisdiction, under the follow‐
ing conditions:
5.6.3.2 Solenoid valves, where used, both in the fuel line from
the supply or day tank closest to the generator set and in the
water-cooling lines, shall operate from battery voltage.
(1)
5.6.3.2.1 Solenoid valves shall have a manual (nonelectric)
operation, or a manual bypass valve shall be provided.
(3)
5.6.3.2.1.1 The manual bypass valve shall be visible and acces‐
sible and its purpose identified.
5.6.3.2.1.2 The fuel bypass valve shall not be the valve used for
malfunction or emergency shutdown.
5.6.3.3 The prime mover shall be provided with the following
instruments:
(1)
(2)
(3)
(4)
(5)
Oil pressure gauge to indicate lubricating oil pressure
when a pressurized lubricating system is provided
Temperature gauge to indicate cooling medium tempera‐
ture when a liquid medium cooling system is used
Hour meter to indicate actual total running time
Battery-charging meter indicating performance of prime
mover–driven battery charging means
Other instruments as recommended or provided by the
prime mover manufacturer where required for mainte‐
nance
5.6.3.4 The instruments required in 5.6.3.3(1) through
5.6.3.3(4) shall be placed on an enclosed panel, located in
proximity to or on the energy converter, in a location that
allows maintenance personnel to observe them readily. The
enclosed panel shall be mounted by means of antishock vibra‐
tion mountings if mounted on the energy converter.
5.6.3.5 All wiring for connection to the control panel shall be
harnessed or flexibly enclosed, shall be securely mounted on
the prime mover to prevent chafing and vibration damage, and
shall terminate at the control panel in an enclosed box or
panel. (For control panel requirements, see 5.6.5.)
5.6.3.6 The generator set shall be fitted with an integral acces‐
sory battery charger, driven by the prime mover and automatic
voltage regulator, and capable of charging and maintaining the
starting battery unit (and control battery, where used) in a fully
charged condition during a running condition.
5.6.3.6.1 A battery charger driven by the prime mover shall
not be required for Level 2 generators, provided the automatic
battery charger has a high-low rate capable of fully charging
the starting battery within the time frame required by this
standard while powering all loads connected to the starting
batteries.
5.6.4 Prime Mover Starting Equipment.
5.6.4.1 Starting Systems. Starting shall be accomplished using
either an electric starter or a stored energy starting system.
2019 Edition
(2)
(4)
Where two complete periods of cranking cycles are
completed without replacement of the stored energy
Where a means for automatic restoration from the emer‐
gency source of the stored energy is provided
Where the stored energy system has the cranking capacity
specified in 5.6.4.2.1
Where the stored energy system has a “black start” capa‐
bility in addition to normal discharge capability
5.6.4.2* Otto or Diesel Cycle Prime Movers. For otto or
diesel cycle prime movers, the type and duration of the crank‐
ing cycle shall be as specified in Table 5.6.4.2.
5.6.4.2.1 A complete cranking cycle shall consist of an auto‐
matic crank period of approximately 15 seconds followed by a
rest period of approximately 15 seconds. Upon starting and
running the prime mover, further cranking shall cease.
5.6.4.2.2 Two means of cranking termination shall be utilized
so that one serves as backup to prevent inadvertent starter
engagement.
5.6.4.2.3 Otto cycle prime movers of 15 kW and lower and all
diesel prime movers shall be permitted to use continuous
cranking methods.
5.6.4.3* Number of Batteries. Each prime mover shall be
provided with both of the following:
(1)
(2)
Storage battery units as specified in Table 5.6.4.2
A storage rack for each battery or battery unit
5.6.4.4* Size of Batteries. The battery unit shall have the
capacity to maintain the cranking speed recommended by the
prime mover manufacturer through two complete periods of
cranking limiter time-outs as specified in Table 5.6.4.2, item
(d).
Table 5.6.4.2 Starting Equipment Requirements
Starting Equipment Requirements
(a)
(b)
(c)
(d)
(e)
(f)
(g)
Battery unit
Battery certification
Cycle cranking
Cranking limiter time-outs
Cycle crank (3 cycles)
Continuous crank
Float-type battery charger
dc ammeter
dc voltmeter
Recharge time
Low battery voltage alarm
contacts
X: Required. O: Optional. NA: Not applicable.
Level 1
Level 2
X
X
O
X
NA
O
75 sec
45 sec
X
X
X
24 hr
X
75 sec
45 sec
X
X
X
36 hr
X
EMERGENCY POWER SUPPLY (EPS): ENERGY SOURCES, CONVERTERS, AND ACCESSORIES
5.6.4.5 Type of Battery. The battery shall be of the nickelcadmium or lead-acid type.
5.6.4.5.1* Lead-acid batteries shall be furnished as charged
when wet. Drain-dry batteries or dry-charged lead-acid batteries
shall be permitted.
5.6.4.5.2 When furnished, vented nickel-cadmium batteries
shall be filled and charged and shall have listed flip-top, flame
arrester vent caps.
mounts, if required, to maximize reliability. An automatic
control and safety panel shall be a part of the EPS containing
the following equipment or possess the following characteris‐
tics, or both:
(1)
(2)
(3)
5.6.4.5.5 All batteries used in this service shall have been
designed for this duty and shall have demonstrable characteris‐
tics of performance and reliability acceptable to the authority
having jurisdiction.
(4)
(2)
(3)
(4)
At its rated voltage, the charger shall be capable of deliv‐
ering energy into a fully discharged battery unit without
damaging the battery.
The charger shall be capable of returning the fully
discharged battery to 100 percent of its ampere-hour
rating within the time specified in Table 5.6.4.2, item (f).
As specified in Table 5.6.4.2, item (e), meters with an
accuracy within 5 percent of range shall be furnished.
The charger shall be permanently marked with the
following:
(a)
(5)
(6)
Allowable range of battery unit capacity that can be
recharged within the time requirements of Table
5.6.4.2
(b) Nominal output current and voltage
(c) Sufficient battery-type data to allow replacement
batteries to be obtained
The battery charger output and performance shall be
compatible with the batteries furnished.
Battery chargers used in Level 1 systems shall include
temperature compensation for charge rate.
5.6.5 Control Functions.
5.6.5.1 A control panel shall be provided and shall contain the
following:
(1)
(2)
(3)
(4)
(5)
Automatic remote start capability
“Run-off-automatic” switch function
Shutdowns as required by 5.6.5.2(3)
Alarms as required by 5.6.5.2(4)
Controls as required by 5.6.5.2(5)
5.6.5.2 Where a control panel is mounted on the energy
converter, it shall be mounted by means of antivibration shock
Failing to start after specified cranking time
Overspeed
Low lubricating-oil pressure
High engine temperature (An automatic engine
shutdown device for high lubricating-oil tempera‐
ture shall not be required.)
(e) Operation of remote manual stop station
Individual alarm indication to annunciate any of the
conditions listed in Table 5.6.5.2 and with the following
characteristics:
(a)
(b)
(c)
5.6.4.7 All chargers shall include the following characteristics,
which are to be accomplished without manual intervention
(i.e., manual switch or manual tap changing):
(1)
Run: Manually initiate, start, and run prime mover
Off: Stop prime mover or reset safeties, or both
Automatic: Allow prime mover to start or stop by
operating a remote contact.
Controls to shut down and lock out the prime mover
under any of the following conditions:
(a)
(b)
(c)
(d)
5.6.4.5.6 Batteries shall be prepared for use according to the
battery manufacturer's instructions.
5.6.4.6* Automatic Battery Charger. In addition to the prime
mover– (engine-) driven charger required in 5.6.3.6.1, a battery
charger(s), as required in Table 5.6.4.2, shall be supplied for
maintaining a charge on both the starting and control battery
unit.
Cranking control equipment to provide the complete
cranking cycle described in 5.6.4.2 and required by Table
5.6.4.2
Panel-mounted control switch(es) marked “run-offautomatic” to perform the following functions:
(a)
(b)
(c)
5.6.4.5.3 The manufacturer shall provide installation, opera‐
tion, and maintenance instructions and, for batteries shipped
dry, electrolyte mixing instructions.
5.6.4.5.4 Batteries shall not be installed until the battery
charger is in service.
110-11
(5)
(6)
Battery powered
Visually indicated
Have additional contacts or circuits for a common
audible alarm that signals locally and remotely
when any of the itemized conditions occurs
(d) Have a lamp test switch(es) to test the operation of
all alarm lamps
Controls to shut down the prime mover upon removal of
the initiating signal or manual emergency shutdown
The ac instruments listed in 5.6.9.9
5.6.5.3 Engines equipped with a maintaining shutdown device
(air shutdown damper) shall have a set of contacts that moni‐
tor the position of this device, with local alarm indication and
remote annunciation in accordance with Table 5.6.5.2.
5.6.5.4 The control panel in 5.6.5.2(4) shall be specifically
approved for either a Level 1 or a Level 2 EPS consistent with
the installation.
5.6.5.5 The cranking cycle shall be capable of being initiated
by any of the following:
(1)
(2)
(3)
(4)
(5)
Manual start initiation as specified in 5.6.5.2(2)(a).
Loss of normal power at any automatic transfer switch
(ATS) as part of the EPSS. Prime mover shall start after
appropriate time delays, upon operation of a remote
switch or set of contacts.
Clock exerciser located in an ATS or in the control panel.
Manually operated (test) switch located in each ATS that
simulates a loss of power and causes automatic starting
and operation until this switch is reset, to cause the
engine circuit to duplicate its functions in the same
manner commercial power is restored after a true
commercial power failure.
Where an ATS is not used, a signal indicating loss of
acceptable power.
5.6.5.6 All installations shall be provided with at least one
remote emergency stop switch for each prime mover.
2019 Edition
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EMERGENCY AND STANDBY POWER SYSTEMS
Table 5.6.5.2 Safety Indications and Shutdowns
Level 1
Level 2
Indicator Function (at Battery Voltage)
CV
S
RA
CV
S
RA
(a) Overcrank
(b) Low water temperature
(c) High engine temperature pre-alarm
(d) High engine temperature
(e) Low lube oil pressure
X
X
X
X
X
X
NA
NA
X
X
X
X
X
X
X
X
X
O
X
X
X
NA
NA
X
X
O
O
NA
O
O
(f) Overspeed
(g) Low fuel main tank
(h) Low coolant level
(i) EPS supplying load
(j) Control switch not in automatic position
X
X
X
X
X
X
NA
O
NA
NA
X
X
X
NA
X
X
O
X
O
X
X
NA
O
NA
NA
O
O
X
NA
X
(k) High battery voltage
(l) Low cranking voltage
(m) Low voltage in battery
(n) Battery charger ac failure
(o) Lamp test
X
X
X
X
X
NA
NA
NA
NA
NA
NA
X
NA
NA
NA
O
O
O
O
X
NA
NA
NA
NA
NA
NA
O
NA
NA
NA
X
NA
X
X
X
NA
NA
NA
NA
NA
X
X
X
X
NA
NA
X
NA
X
NA
O
O
X
NA
NA
NA
NA
NA
X
X
X
O
NA
NA
O
NA
(p) Contacts for local and remote common alarm
(q) Audible alarm silencing switch
(r) Low starting air pressure
(s) Low starting hydraulic pressure
(t) Air shutdown damper when used
(u) Remote emergency stop
CV: Control panel–mounted visual. S: Shutdown of EPS. RA: Remote audible. X: Required. O: Optional. NA: Not applicable.
Notes:
(1) Item (p) shall be provided, but a separate remote audible signal shall not be required when the regular work site in 5.6.6 is staffed 24 hours a day.
(2) Item (b) is not required for combustion turbines.
(3) Item (r) or (s) shall apply only where used as a starting method.
(4) Item (i) EPS ac ammeter shall be permitted for this function.
(5) All required CV functions shall be visually annunciated by a remote, common visual indicator.
(6) All required functions indicated in the RA column shall be annunciated by a remote, common audible alarm as required in 5.6.5.2(4).
(7) Item (g) on gaseous systems shall require a low gas pressure alarm.
(8) Item (b) shall be set at 11°C (20°F) below the regulated temperature determined by the EPS manufacturer as required in 5.3.1.
(2)
For Level 2 EPS, local annunciation
5.6.5.6.1 The remote emergency stop switch shall be located
outside the room housing the prime mover or exterior enclo‐
sure and shall be permitted to be mounted on the exterior of
the enclosure.
5.6.6.3 For the purposes of defining the types of annunciation
in 5.6.6.2, the following shall apply:
5.6.5.6.2 Provisions shall be made so access is limited to quali‐
fied persons.
(2)
5.6.5.6.3 The remote emergency stop switch shall identify the
prime mover it controls.
5.6.6* Remote Controls and Alarms. A remote, common
audible alarm shall be provided as specified in 5.6.5.2(4).
5.6.6.1 Alarms and annunciation shall be powered by the
prime mover starting battery unless operational constraints
make this impracticable. In that circumstance an alternate
source from the EPS, such as a storage battery, UPS, or branch
circuit supplied by the EPSS, shall be permitted.
5.6.6.2 The following annunciation shall be provided at a
minimum:
(1)
For Level 1 EPS, local annunciation and facility remote
annunciation, or local annunciation and network remote
annunciation
2019 Edition
(1)
(3)
Local annunciation is located on the equipment itself or
within the same equipment room.
Facility remote annunciation is located on site but not
within the room where the equipment is located.
Network remote annunciation is located off site.
5.6.6.4 An alarm-silencing means shall be provided, and the
panel shall include repetitive alarm circuitry so that, after the
audible alarm has been silenced, it reactivates after the fault
condition has been cleared and has to be restored to its normal
position to be silenced again.
5.6.6.5 In lieu of the requirement in 5.6.6.4, a manual alarmsilencing means shall be permitted that silences the audible
alarm after the occurrence of the alarm condition, provided
such means do not inhibit any subsequent alarms from sound‐
ing the audible alarm again without further manual action.
5.6.7 Prime Mover Cooling Systems. Cooling systems for
prime movers shall be either forced-air or natural convection,
liquid-cooled, or a combination thereof.
EMERGENCY POWER SUPPLY (EPS): ENERGY SOURCES, CONVERTERS, AND ACCESSORIES
5.6.7.1 Forced-air-cooled diesel or otto cycle engines shall
have an integral fan selected to cool the prime mover under
full load conditions.
5.6.7.2 Liquid-cooled prime movers for Level 1 applications
shall be arranged for closed-loop cooling and consist of one of
the following types:
(1)
(2)
(3)
Unit-mounted radiator and fan
Remote radiator
Heat exchanger (liquid-to-liquid)
5.6.7.3 Cooling systems shall prevent overheating of prime
movers under conditions of highest anticipated ambient
temperature at the installed elevation (above sea level) when
fully loaded.
5.6.7.4* Power for fans and pumps on remote radiators and
heat exchangers shall be supplied from a tap at the EPS output
terminals or ahead of the first load circuit overcurrent protec‐
tive device.
5.6.7.5 The secondary side of heat exchangers shall be a
closed-loop cycle, that is, one that recycles the cooling agent.
5.6.7.6 The installed EPS cooling system shall be designed to
cool the prime mover at full-rated load while operating in the
particular installation circumstances of each EPS.
5.6.7.7 A full-load on-site test shall not result in activation of
high-temperature pre-alarm or high-temperature shutdown.
5.6.7.8 For EPSS cooling systems requiring intermittent or
continuous waterflow or pressure, or both, a utility, city, or
other water supply service shall not be used.
5.6.7.9 The EPSS cooling system shall be permitted to use util‐
ity or city water for filling or makeup water.
5.6.7.10 Design of the EPS cooling system shall consider the
following factors:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
Remote radiator or heat exchanger sizing
Pipe sizing
Pump sizing
Sufficient shutoffs to isolate equipment to facilitate main‐
tenance
The need for and sizing of de-aeration and surge tanks
Drain valves for cleaning and flushing the cooling system
Type of flexible hoses between the prime mover and the
cooling system piping
110-13
5.6.9.4 EPS voltage output, or the output of the transformer
immediately down-line from the EPS, at full load shall match
the nominal voltage of the normal source at the transfer
switch(es).
5.6.9.5 Exciters, where furnished, shall be of either the rotat‐
ing type or the static type.
5.6.9.6 Voltage regulators shall be capable of responding to
load changes to meet the system stability requirements of
5.6.9.8.
5.6.9.7 If the system stability requirements of 5.6.9.8 cannot be
accomplished, anti-hunt provisions shall be included.
5.6.9.8 Generator system performance (i.e., prime mover,
generator, exciter, and voltage regulator, as applicable when
prototype tested as specified in 5.2.1.2) shall be as follows:
(1)
(2)
(3)
(4)
Stable voltage and frequency at all loads shall be provided
to full-rated loads.
Values consistent with the user's needs for frequency
droop and voltage droop shall be maintained.
Voltage dip at the generator terminals for the maximum
anticipated load change shall not cause disruption or
relay dropout in the load.
Frequency dip and restoration to steady state for any
sudden load change shall not exceed the user's specified
need.
5.6.9.9 The generator instrument panel for Level 1 applica‐
tions shall contain the following:
(1)
(2)
(3)
(4)
(5)
An ac voltmeter(s) for each phase or a phase selector
switch
An ac ammeter(s) for each phase or a phase selector
switch
A frequency meter
A voltage-adjusting feature to allow ±5 percent voltage
adjustment
An ac kW or kVA meter to show total load on the genera‐
tor set
5.6.10 Miscellaneous Requirements.
5.6.10.1 Where applicable, the prime mover and generator
shall be factory mounted on a common base, rigid enough to
maintain the dynamic alignment of the rotating element of the
system prior to shipment to the installation site.
5.6.8 Prime Mover Exhaust Piping. Where applicable, the
exhaust system shall include a muffler or silencer sized for the
unit and a flexible exhaust section.
5.6.10.2 A certification shall be supplied with the unit that
verifies the torsional vibration compatibility of the rotating
element of the prime mover and generator for the intended
use of the energy converter.
5.6.9 Generators, Exciters, and Voltage Regulators. Genera‐
tors shall comply with Article 445 of NFPA 70 and with the
requirements of 5.6.9.1 through 5.6.9.9.
5.6.10.3* Vibration isolators shall be furnished where neces‐
sary to minimize vibration transmission to the permanent struc‐
ture.
5.6.9.1* The generator shall be of dripproof construction and
have amortisseur windings.
5.6.10.4 The manufacturer of the EPS shall submit complete
schematic, wiring, and interconnection diagrams showing all
terminal and destination markings for all EPS equipment, as
well as the functional relationship between all electrical compo‐
nents.
5.6.9.2 The generator shall be suitable for the environmental
conditions at the installation location.
5.6.9.3 The generator systems shall be factory tested as a unit
to ensure operational integrity of all of the following:
(1)
(2)
(3)
Generator
Exciter
Voltage regulator
5.6.10.5 The energy converter supplier shall stipulate compli‐
ance and performance with this standard for the entire unit
when installed.
5.6.10.6 Where requested, the short circuit current capability
at the generator output terminals shall be furnished.
2019 Edition
110-14
EMERGENCY AND STANDBY POWER SYSTEMS
Chapter 6 Transfer Switch Equipment
6.1 General.
6.1.1* Switches shall transfer electric loads from one power
source to another.
6.1.2* The electrical rating shall be sized for the total load
that is designed to be connected.
6.1.3 Each switch shall be in a separate enclosure or compart‐
ment.
6.1.4 The switch, including all load current-carrying compo‐
nents, shall be listed for all load types to be served.
6.1.5 The switch, including all load current-carrying compo‐
nents, shall be designed to withstand the effects of available
fault currents.
6.2.4* Manual Operation. Instruction and equipment shall be
provided for safe manual nonelectric transfer in the event the
transfer switch malfunctions.
6.2.5* Time Delay on Starting of EPS. A time-delay device
shall be provided to delay starting of the EPS. The timer shall
prevent nuisance starting of the EPS and possible subsequent
load transfer in the event of momentary power dips and inter‐
ruptions of the primary source.
6.2.6 Time Delay at Engine Control Panel. Time delays shall
be permitted to be located at the engine control panel in lieu
of in the transfer switches.
6.2.7 Time Delay on Transfer to EPS. An adjustable timedelay device shall be provided to delay transfer and sequence
load transfer to the EPS to avoid excessive voltage drop when
the transfer switch is installed for Level 1 use.
6.1.6* Where available, each switch shall be listed for emer‐
gency service as a completely factory-assembled and factorytested apparatus. Medium voltage transfer of central plant or
mechanical equipment not including life safety, emergency, or
critical branch loads shall be permitted to be transferred by
electrically interlocked medium voltage circuit breakers.
6.2.7.1 Time Delay Commencement. The time delay shall
commence when proper EPS voltage and frequency are
achieved.
6.2 ATS Features.
6.2.8* Time Delay on Retransfer to Primary Source. An
adjustable time-delay device with automatic bypass shall be
provided to delay retransfer from the EPS to the primary
source of power and to allow the normal source to stabilize
before retransfer of the load.
6.2.1* General. Automatic transfer switches shall be capable
of all of the following:
(1)
(2)
(3)
Electrical operation and mechanical holding
Transfer and retransfer of the load automatically
Visual annunciation when “not-in-automatic”
6.2.2 Source Monitoring.
6.2.2.1* Undervoltage-sensing devices shall be provided to
monitor all ungrounded lines of the normal source of power as
follows:
(1)
When the voltage on any phase falls below the minimum
operating voltage of any load to be served, the transfer
switch shall automatically initiate engine start and the
process of transfer to the EPS.
(2)* When the voltage on all phases of the normal source
returns to within specified limits for a designated period
of time, the process of transfer back to normal power
shall be initiated.
6.2.2.2 Both voltage-sensing and frequency-sensing equipment
shall be provided to monitor one ungrounded line of the EPS.
6.2.2.3 Transfer to the EPS shall be inhibited until the voltage
and frequency are within a specified range to handle loads to
be served.
6.2.2.3.1 Sensing equipment shall not be required in the
transfer switch, provided it is included with the engine control
panel.
6.2.2.3.2 Frequency-sensing equipment shall not be required
for monitoring the public utility source where used as an EPS,
as permitted by 5.1.3.
6.2.3* Interlocking. Mechanical interlocking or an approved
alternate method shall prevent the inadvertent interconnection
of the normal power supply and the EPS, or any two separate
sources of power.
2019 Edition
6.2.7.2 Time Delay at Engine Control Panel. Time delays shall
be permitted to be located at the engine control panel in lieu
of in the transfer switches.
6.2.9 Time Delay Bypass If EPS Fails. The time delay shall be
automatically bypassed if the EPS fails.
6.2.9.1 The transfer switch shall be permitted to be program‐
med for a manually initiated retransfer to the normal source to
provide for a planned momentary interruption of the load.
6.2.9.2 If used, the arrangement in 6.2.9.1 shall be provided
with a bypass feature to allow automatic retransfer in the event
that the EPS fails and the normal source is available.
6.2.10 Time Delay on Engine Shutdown. A minimum time
delay of 5 minutes shall be provided for unloaded running of
the EPS prior to shutdown to allow for engine cooldown.
6.2.10.1 The minimum 5-minute delay shall not be required
on small (15 kW or less) air-cooled prime movers.
6.2.10.2 A time-delay device shall not be required, provided it
is included with the engine control panel, or if a utility feeder
is used as an EPS.
6.2.11 Engine Generator Exercising Timer. A program timing
device shall be provided to exercise the EPS as described in
Chapter 8.
6.2.11.1 Transfer switches shall transfer the connected load to
the EPS and immediately return to normal power automatically
in case of an EPS failure.
6.2.11.2 Exercising timers shall be permitted to be located at
the engine control panel in lieu of in the transfer switches.
6.2.11.3 A program timing device shall not be required in
health care facilities that provide scheduled testing in accord‐
ance with NFPA 99.
INSTALLATION AND ENVIRONMENTAL CONSIDERATIONS
6.2.12 Test Switch. A test means shall be provided on each
ATS that simulates failure of the normal power source and
then transfers the load to the EPS.
6.2.13* Indication of Transfer Switch Position. Two pilot
lights with identification nameplates or other approved posi‐
tion indicators shall be provided to indicate the transfer switch
position.
6.2.14 Motor Load Transfer. Provisions shall be included to
reduce currents resulting from motor load transfer if such
currents could damage EPSS equipment or cause nuisance trip‐
ping of EPSS overcurrent protective devices.
6.2.15* Isolation of Neutral Conductors. Provisions shall be
included for ensuring continuity, transfer, and isolation of the
primary and the EPS neutral conductors wherever they are
separately grounded to achieve ground-fault sensing.
6.2.16* Nonautomatic Transfer Switch Features. Switching
devices shall be mechanically held and shall be operated by
direct manual or electrical remote manual control.
6.2.16.1 Interlocking. Reliable mechanical interlocking or an
approved alternate method shall prevent the inadvertent inter‐
connection of the normal power source and the EPS.
6.2.16.2 Indication of Transfer Switch Position. Two pilot
lights with identification nameplates or other approved posi‐
tion indicators shall be provided to indicate the switch position.
6.3 Requirements for Paralleled Generator Sets. When two or
more engine generator sets are paralleled for emergency
power, the paralleled system is the source, and system logic
shall be arranged to manage the loads to maintain power qual‐
ity.
6.3.1 The transfer of loads to the EPS shall be sequenced as
follows:
(1)
(2)
(3)
First-priority loads shall be switched to the emergency bus
upon sensing the availability of emergency power on the
bus.
Each time an additional engine generator set is connec‐
ted to the bus, a remaining load shall be connected in
order of priority until all emergency loads are connected
to the bus.
The system shall be designed so that, upon failure of one
or more engine generator sets, the load is automatically
reduced, starting with the load of least priority and
proceeding in ascending priority, so that the last load
affected is the highest-priority load.
6.4 Bypass-Isolation Switches.
6.4.1 Bypassing and Isolating Transfer Switches. Bypassisolation switches shall be permitted for bypassing and isolating
the transfer switch and shall be installed in accordance with
6.4.2, 6.4.3, and 6.4.4.
6.4.2 Bypass-Isolation Switch Rating. The bypass-isolation
switch shall have a continuous current rating and a current
rating compatible with that of the associated transfer switch.
6.4.3* Bypass-Isolation Switch Classification. Each bypassisolation switch shall be listed for emergency electrical service
as a completely factory-assembled and factory-tested apparatus.
6.4.4* Operation. With the transfer switch isolated or discon‐
nected, the bypass-isolation switch shall be designed so it can
110-15
function as an independent nonautomatic transfer switch and
allow the load to be connected to either power source.
6.4.5 Reconnection of Transfer Switch. Reconnection of the
transfer switch shall be possible without a load interruption
greater than the maximum time, in seconds, specified by the
type of system.
6.5 Protection.
6.5.1* General. The overcurrent protective devices in the
EPSS shall be coordinated to optimize selective tripping of the
circuit overcurrent protective devices when a short circuit
occurs.
6.5.2 Short Circuit Current. The maximum available short
circuit current from both the utility source and the emergency
energy source shall be evaluated for the ability to satisfy this
coordination capability.
6.5.3* Overcurrent Protective Device Rating. The overcur‐
rent protective device shall have an interrupting rating equal to
or greater than the maximum available short circuit current at
its location.
6.5.4 Accessibility. Overcurrent devices in EPSS circuits shall
be accessible to authorized persons only.
Chapter 7 Installation and Environmental Considerations
7.1 General.
7.1.1* This chapter shall establish minimum requirements
and considerations relative to the installation and environmen‐
tal conditions that have an effect on the performance of the
EPSS equipment such as the following:
(1)
(2)
(3)
(4)
Geographic location
Building type
Classification of occupancy
Hazard of contents
7.1.2* Minimizing the probability of equipment or cable fail‐
ure within the EPSS shall be a design consideration to reduce
the disruption of loads served by the EPSS.
7.1.3 The EPSS equipment shall be installed as required to
meet the user’s needs and to be in accordance with all of the
following:
(1)
(2)
(3)
This standard
The manufacturer’s specifications
The authority having jurisdiction
7.1.4 EPSS equipment installed for the various levels of service
defined in this standard shall be designed and assembled for
such service.
7.1.5 When the normal power source is not available, the EPS
shall be permitted to serve optional loads other than system
loads, provided that the EPS has adequate capacity or auto‐
matic selective load pickup and load shedding are provided as
needed to ensure adequate power to (1) the Level 1 loads, (2)
the Level 2 loads, and (3) the optional loads, in that order of
priority. When normal power is available, the EPS shall be
permitted to be used for other purposes such as peak load shav‐
ing, internal voltage control, load relief for the utility providing
normal power, or cogeneration.
2019 Edition
110-16
EMERGENCY AND STANDBY POWER SYSTEMS
7.2 Location.
7.2.1 Indoor EPS Installations. The EPS shall be installed in a
separate room for Level 1 installations.
7.2.1.1 The EPS room shall be separated from the rest of the
building by construction with a 2-hour fire resistance rating.
7.2.1.2 EPSS equipment shall be permitted to be installed in
the EPS room.
7.2.1.3 No other equipment, including architectural appurte‐
nances, except those that serve this space, shall be permitted in
the EPS room.
7.2.2 Outdoor EPS Installations.
7.2.2.1 The EPS shall be installed in a suitable enclosure loca‐
ted outside the building and capable of resisting the entrance
of snow or rain at a maximum wind velocity as required by local
building codes.
7.2.2.2 EPSS equipment shall be permitted to be installed in
the EPS enclosure.
specified by a requirement recognized by the authority having
jurisdiction.
7.4 Mounting.
7.4.1 Rotating energy converters shall be installed on solid
foundations to prohibit sagging of fuel, exhaust, or lubricatingoil piping and damage to parts resulting in leakage at joints.
7.4.1.1 Such foundations or structural bases shall raise the
engine at least 150 mm (6 in.) above the floor or grade level
and be of sufficient elevation to facilitate lubricating-oil drain‐
age and ease of maintenance.
7.4.2 Foundations shall be of the size (mass) and type recom‐
mended by the energy converter manufacturer.
7.4.3 Where required to prevent transmission of vibration
during operation, the foundation shall be isolated from the
surrounding floor or other foundations, or both, in accordance
with the manufacturer's recommendations and accepted struc‐
tural engineering practices.
7.2.2.3 No other equipment, including architectural appurte‐
nances, except those that serve this space, shall be permitted in
the EPS enclosure.
7.4.4 The EPS shall be mounted on a fabricated metal skid
base of the type that shall resist damage during shipping and
handling. After installation, the base shall maintain alignment
of the unit during operation.
7.2.3* Level 1 EPSS equipment shall not be installed in the
same room with the normal service equipment, where the serv‐
ice equipment is rated over 150 volts to ground and equal to or
greater than 1000 amperes.
7.5* Vibration. Vibration isolators, as recommended by the
manufacturer of the EPS, shall be installed either between the
rotating equipment and its skid base or between the skid base
and the foundation or inertia base.
7.2.4* The rooms, enclosures, or separate buildings housing
Level 1 or Level 2 EPSS equipment shall be designed and loca‐
ted to minimize damage from flooding, including that caused
by the following:
7.6* Noise. Design shall include consideration of noise
control regulations.
(1)
(2)
(3)
Flooding resulting from fire fighting
Sewer water backup
Other disasters or occurrences
7.2.5* Minimizing the possibility of damage resulting from
interruptions of the emergency source shall be a design consid‐
eration for EPSS equipment.
7.2.6 The EPS equipment shall be installed in a location that
permits ready accessibility and a minimum of 0.9 m (36 in.)
from the skid rails' outermost point in the direction of access
for inspection, repair, maintenance, cleaning, or replacement.
This requirement shall not apply to units in outdoor housings.
7.2.7 Design considerations shall minimize the effect of the
failure of one energy converter on the continued operation of
other units.
7.3 Lighting.
7.3.1 The Level 1 or Level 2 EPS equipment location(s) shall
be provided with battery-powered emergency lighting. This
requirement shall not apply to units located outdoors in enclo‐
sures that do not include walk-in access.
7.3.2 The emergency lighting charging system and the normal
service room lighting shall be supplied from the load side of
the transfer switch.
7.3.3* The minimum average horizontal illumination provi‐
ded by normal lighting sources in the separate building or
room housing the EPS equipment for Level 1 shall be 32.3 lux
(3.0 ft-candles) measured at the floor level, unless otherwise
2019 Edition
7.7 Heating, Cooling, and Ventilating.
7.7.1* With the EPS running at rated load, ventilation airflow
shall be provided to limit the maximum air temperature in the
EPS room or the enclosure housing the unit to the maximum
ambient air temperature required by the EPS manufacturer.
7.7.1.1 Consideration shall be given to all the heat emitted to
the EPS equipment room by the energy converter, uninsulated
or insulated exhaust pipes, and other heat-producing equip‐
ment.
7.7.2 Air shall be supplied to the EPS equipment for combus‐
tion.
7.7.2.1* For EPS supplying Level 1 EPSS, ventilation air shall
be supplied directly from a source outside the building by an
exterior wall opening or from a source outside the building by
a 2-hour fire-rated air transfer system.
7.7.2.2 For EPS supplying Level 1 EPSS, discharge air shall be
directed outside the building by an exterior wall opening or to
an exterior opening by a 2-hour fire-rated air transfer system.
7.7.2.3 Fire dampers, shutters, or other self-closing devices
shall not be permitted in ventilation openings or ductwork for
supply or return/discharge air to EPS equipment for Level 1
EPSS.
7.7.3 Ventilation air supply shall be from outdoors or from a
source outside the building by an exterior wall opening or
from a source outside the building by a 2-hour fire-rated air
transfer system.
INSTALLATION AND ENVIRONMENTAL CONSIDERATIONS
110-17
7.7.4 Ventilation air shall be provided to supply and discharge
cooling air for radiator cooling of the EPS when running at
rated load.
7.9.3 Fuel piping shall be of compatible metal to minimize
electrolysis and shall be properly sized, with vent and fill pipes
located to prevent entry of groundwater or rain into the tank.
7.7.4.1 Ventilation air supply and discharge for radiatorcooled EPS shall have a maximum static restriction of 125 Pa
(0.5 in. of water column) in the discharge duct at the radiator
outlet.
7.9.3.1* Galvanized fuel lines shall not be used.
7.9.3.2 Approved flexible fuel lines shall be used between the
prime mover and the fuel piping.
7.7.4.2 Radiator air discharge shall be ducted outdoors or to
an exterior opening by a 2-hour rated air transfer system.
7.9.4 Day tanks on diesel systems shall be installed below the
engine fuel return elevation.
7.7.5 Motor-operated dampers, when used, shall be spring
operated to open and motor closed. Fire dampers, shutters, or
other self-closing devices shall not be permitted in ventilation
openings or ductwork for supply or return/discharge air to
EPS equipment for Level 1 EPSS.
7.9.4.1 The return line to the day tank shall be below the fuel
return elevation.
7.7.6 Units housed outdoors shall be heated as specified in
5.3.5.
7.7.7 Design of the heating, cooling, and ventilation system
for the EPS equipment room shall include provision for factors
including, but not limited to, the following:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
Heat
Cold
Dust
Humidity
Snow and ice accumulations around housings
Louvers
Remote radiator fans
Prevailing winds blowing against radiator fan discharge
air
7.8 Installed EPS Cooling System.
7.8.1 Makeup water hose bibs and floor drains, where
required by other codes and standards, shall be installed in EPS
equipment rooms.
7.8.2 Where duct connections are used between the prime
mover radiator and air-out louvers, the ducts shall be connec‐
ted to the prime movers by means of flexible sections.
7.9 Fuel System.
7.9.1 Fuel tanks shall be sized to accommodate the specific
EPS class.
7.9.1.1* All fuel tanks and systems shall be installed and main‐
tained in accordance with NFPA 30, NFPA 37, NFPA 54, and
NFPA 58.
7.9.1.2* Fuel system design shall provide for a supply of clean
fuel to the prime mover.
7.9.1.3 Tanks shall be sized so that the fuel is consumed within
the storage life, or provisions shall be made to remediate fuel
that is stale or contaminated or to replace stale or contamina‐
ted fuel with clean fuel.
7.9.4.2 Gravity fuel oil return lines between the day tank and
the main supply tank shall be sized to handle the potential fuel
flow and shall be free of traps so that fuel can flow freely to the
main tank.
7.9.5 Integral tanks of the following capacities shall be permit‐
ted inside or on roofs of structures, or as approved by the
authority having jurisdiction:
(1)
(2)
Maximum of 2498 L (660 gal) diesel fuel
Maximum of 95 L (25 gal) gasoline fuel
7.9.6* The fuel supply for gas-fueled and liquid-fueled prime
movers shall be installed in accordance with applicable stand‐
ards.
7.9.7* Where the gas supply is connected to the building gas
supply system, it shall be connected on the supply side of the
main gas shutoff valve and marked as supplying an emergency
generator.
7.9.8 The building's main gas shutoff valve shall be marked or
tagged to indicate the existence of the separate EPS shutoff
valve.
7.9.9 The fuel supply for gas-fueled and liquid-fueled prime
movers shall be designed to meet the demands of the prime
mover for all of the following factors:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
Sizing of fuel lines
Valves, including manual shutoff
Battery-powered fuel solenoids
Gas regulators
Regulator vent piping
Flexible fuel line section
Fuel line filters
Fuel vaporizers (LP-Gas)
Ambient temperature effect of fuel tank vaporization
rates of LP-Gas where applicable
7.9.10 The fuel storage and supply lines for an EPSS shall be
in accordance with this standard or with the specific authority
having jurisdiction, or both.
7.9.11 All manual fuel system valves shall be of the indicating
type.
7.9.2 Fuel tanks shall be close enough to the prime mover for
the fuel lift (suction head) of the prime mover fuel pump to
meet the fuel system requirements, or a fuel transfer pump and
day tank shall be provided.
7.9.12 Listed generator subbase secondary containment fuel
tanks of 2498 L (660 gal) capacity and below shall be permitted
to be installed outdoors or indoors without diking or remote
impounding.
7.9.2.1 If the engine manufacturer's fuel pump static head
pressure limits are exceeded when the level of fuel in the tank
is at a maximum, a day tank shall be utilized.
7.9.12.1 A minimum clearance of 0.9 m (36 in.) shall be main‐
tained on all sides.
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EMERGENCY AND STANDBY POWER SYSTEMS
7.9.13 Automatically actuated valves shall not be permitted in
the fuel oil supply or fuel oil return lines for Level 1 emergency
power supply systems.
7.11.2* Where fire suppression systems are installed in EPS
equipment rooms or separate buildings, the following systems
shall not be used:
7.10 Exhaust System.
(1)
7.10.1 The exhaust system equipment and installation, includ‐
ing piping, muffler, and related accessories, shall be in accord‐
ance with NFPA 37 and other applicable standards.
(2)
7.10.2 Exhaust system installation shall be gastight to prevent
exhaust gas fumes from entering inhabited rooms or buildings
and terminate in such a manner that toxic fumes cannot reen‐
ter a building or structure, particularly through windows, air
ventilation inlets, or the engine air-intake system.
7.10.3* Exhaust piping shall be connected to the prime mover
by means of a flexible connector and shall be independently
supported thereafter so that no damaging weight or stress is
applied to the engine exhaust manifold or turbocharger.
7.10.3.1 A condensate trap and drain valve shall be provided
at the low point(s) of the piping unless the piping is selfdraining.
7.10.3.2 Design consideration shall be given to thermal expan‐
sion and the resultant movement of the piping.
7.10.3.3 For reciprocating engines, mufflers shall be placed as
close as practicable to the engine, in a horizontal position if
possible.
7.10.3.4 An approved thimble(s) shall be used where exhaust
piping passes through combustible walls or partitions.
7.10.3.5 For reciprocating engines, the piping shall terminate
in any of the following:
(1)
(2)
(3)
(4)
Rain cap
Tee
Ell, pointing downwind from the prevailing wind
Vertically upward-oriented stack with suitable provisions
for trapping and draining rain and snow water
7.10.3.6 Design consideration shall be given to the potential
heat effect due to proximity to all of the following:
(1)
(2)
(3)
Conduit runs
Fuel piping
Lighting fixtures
7.10.3.7 Design consideration shall be given to insulating the
engine exhaust systems in buildings after the flexible section.
7.10.4 For maximum efficiency, operation economy, and
prevention of engine damage, the exhaust system shall be
designed to eliminate excessive backpressure on the engine by
properly selecting, routing, and installing the piping size,
connections, and muffler.
7.10.4.1 Exhaust systems shall be installed to ensure satisfac‐
tory EPS operation and meet the requirements of the manufac‐
turer.
7.11 Protection.
7.11.1 The room in which the EPS equipment is located shall
not be used for other purposes that are not directly related to
the EPS. Parts, tools, and manuals for routine maintenance and
repair shall be permitted to be stored in the EPS room.
2019 Edition
Carbon dioxide or halon systems, unless prime mover
combustion air is taken from outside the structure
An automatic dry chemical system, unless the manufac‐
turers of the EPS certify that the dry chemical system
cannot damage the EPS system, hinder its operation, or
reduce its output
7.11.3 Where the EPS rooms or separate buildings are equip‐
ped with fire detection systems, the installation shall be in
accordance with NFPA 72.
7.11.4 Where outdoor and/or rooftop Level 1 EPS installa‐
tions are required to be protected from lightning, the lightning
protection system(s) shall be installed in accordance with
NFPA 780.
7.11.5* In recognized seismic risk areas, EPS and EPSS
components, such as electrical distribution lines, water distribu‐
tion lines, fuel distribution lines, and other components that
serve the EPS, shall be designed to minimize damage from
earthquakes and to facilitate repairs if an earthquake occurs.
7.11.6* For systems in seismic risk areas, the EPS, transfer
switches, distribution panels, circuit breakers, and associated
controls shall be capable of performing their intended func‐
tion after being subjected to the anticipated seismic shock.
7.12 Distribution.
7.12.1 The distribution and wiring systems within EPSS shall
be installed in accordance with NFPA 70.
7.12.2 When EPSSs are installed in health care facilities, the
installation of the EPSS shall also be in compliance with
NFPA 99.
7.12.3 If the conduit's point of attachment to the EPS is on
the forcing function side of the EPS vibration isolation system,
a flexible conduit section(s) shall be installed between the EPS
unit(s) and any of the following, so attached:
(1)
(2)
(3)
The transfer switch
The control and annunciator wiring
Any accessory supply wiring such as jacket water heaters
7.12.3.1 Stranded wire of adequate size shall be used to mini‐
mize breakage due to vibration.
7.12.3.2 Bushings shall be installed to protect wiring from
abrasion with conduit terminations.
7.12.4 All ac-powered support and accessory equipment neces‐
sary to the operation of the EPS shall be supplied from the load
side of the ATSs, or the output terminals of the EPS, ahead of
the main EPS overcurrent protection to ensure continuity of
the EPSS operation and performance.
7.12.5 The starting battery units shall be located next to the
prime mover starter to minimize voltage drop.
7.12.5.1 Battery cables shall be sized to minimize voltage drop
in accordance with the manufacturer's recommendations and
accepted engineering practices.
7.12.5.2 Battery charger output wiring shall be permanently
connected to the primary side of the starter solenoid (positive)
and the EPS frame (negative), or other grounding location.
INSTALLATION AND ENVIRONMENTAL CONSIDERATIONS
7.13 Installation Acceptance.
7.13.1 Upon completion of the installation of the EPSS, the
EPS shall be tested to ensure conformity to the requirements of
the standard with respect to both power output and function.
7.13.2 An on-site acceptance test shall be conducted as a final
approval test for all EPSSs.
7.13.2.1 For new Level 1 installations, the EPSS shall not be
considered as meeting this standard until the acceptance tests
have been conducted and test requirements met.
7.13.2.2 The test shall be conducted after completion of the
installation with all EPSS accessory and support equipment in
place and operating.
7.13.3 The authority having jurisdiction shall be given
advance notification of the time at which the acceptance test is
to be performed so that the authority can witness the test.
7.13.4 The EPSS shall perform within the limits specified in
this standard.
7.13.4.1 The on-site installation acceptance test shall be
conducted in accordance with 7.13.4.1.1 through 7.13.4.1.4.
7.13.4.1.1* In a new and unoccupied building or facility, with
the prime mover in a cold start condition and the emergency
load at operating level, a normal power failure shall be initiated
by opening all switches or circuit breakers supplying the
normal power to the building or facility.
7.13.4.1.2* In an existing occupied building or facility, with
the prime mover in a cold start condition and the emergency
load at operating level, a normal power failure shall be simula‐
ted by operating at least one transfer switch test function or
initiated by opening all switches or breakers supplying normal
power to all ATSs that are part of the EPSS being commis‐
sioned by this initial acceptance test.
7.13.4.1.3 When the EPSS consists of paralleled EPSs, the
system control function for paralleling and load shedding shall
be verified in accordance with system design documentation.
7.13.4.1.4 The tests conducted in accordance with 7.13.4.1.1
and 7.13.4.1.2 shall be performed in accordance with
7.13.4.1.4(1) through 7.13.4.1.4(12).
(1) When the EPSS consists of paralleled EPSs, the quantity
of EPSs intended to be operated simultaneously shall be
tested simultaneously with building load for the test
period identified in 7.13.4.1.4(10).
(2) The test load shall be all loads that are served by the
EPSS. There is no minimum loading requirement for
this portion of the test.
(3) The time delay on start shall be observed and recorded.
(4) The cranking time until the prime mover starts and runs
shall be observed and recorded.
(5) The time taken to reach operating speed shall be
observed and recorded.
(6)* The engine start function shall be confirmed by verify‐
ing operation of the initiating circuit of all transfer
switches supplying EPSS loads.
(7) The time taken to achieve a steady-state condition with
all switches transferred to the emergency position shall
be observed and recorded.
(8) The voltage, frequency, and amperes shall be recorded.
(9) Where applicable, the prime mover oil pressure and
water temperature shall be recorded.
110-19
(10) The load test with building load, or other loads that
simulate the intended load as specified in Section 5.4,
shall be continued for not less than 1.5 hours, and the
run time shall be recorded.
(11) When normal power is restored to the building or
facility, the time delay on retransfer to normal power for
each switch with a minimum setting of 5 minutes shall
be recorded.
(12) The time delay on the prime mover cooldown period
and shutdown shall be recorded.
7.13.4.2 After completion of the test performed in 7.13.4.1,
the prime mover shall be allowed to cool for not less than
5 minutes.
7.13.4.3* A load shall be applied for a 2-hour, full-load test.
The building load shall be permitted to serve as part or all of
the load, supplemented by a load bank of sufficient size to
provide a load equal to 100 percent of the nameplate kW
rating of the EPS, less applicable derating factors for site condi‐
tions. With full load applied, the coolant temperature of the
generator set shall stabilize at a constant value relative to
outdoor ambient temperature at least 30 minutes prior to
completion of the test.
7.13.4.3.1* This full-load test shall be initiated after the test
specified in 7.13.4.1.4 by any method that starts the prime
mover and, upon reaching rated rpm, picks up not less than
30 percent of the nameplate kW rating for the first 30 minutes,
not less than 50 percent of the nameplate kW rating for the
next 30 minutes, and 100 percent of the nameplate kW rating
for the next 60 minutes, less applicable derating factors for site
conditions.
7.13.4.3.2 A unity power factor shall be permitted for on-site
testing, provided that rated load tests at the rated power factor
have been performed by the manufacturer of the EPS prior to
shipment.
7.13.4.3.3 Where the EPS is a paralleled multi-unit EPS, each
unit shall be permitted to be tested individually at its rating.
7.13.4.3.4 The data specified in 7.13.4.1.4(4), 7.13.4.1.4(5),
and 7.13.4.1.4(7) shall be recorded at first load acceptance of
the test period identified in 7.13.4.1.4(10).
7.13.4.3.5 The data specified in 7.13.4.1.4(8) and
7.13.4.1.4(9) shall be recorded at first load acceptance and
every 15 minutes thereafter until the completion of the test
period identified in 7.13.4.1.4(10).
7.13.4.4 Any method recommended by the manufacturer for
the cycle crank test shall be utilized to prevent the prime mover
from running.
7.13.4.4.1 The control switch shall be set at “run” to cause the
prime mover to crank.
7.13.4.4.2 The complete crank/rest cycle specified in 5.6.4.2
and Table 5.6.4.2 shall be observed.
7.13.4.4.3 The battery charge rate shall be recorded at 5minute intervals for the first 15 minutes or until charge rate
stabilization.
7.13.4.5 All safeties specified in 5.6.5 and 5.6.6 shall be tested
on site as recommended by the manufacturer.
2019 Edition
110-20
EMERGENCY AND STANDBY POWER SYSTEMS
Exception No. 1: It shall be permitted for the manufacturer to test and
document overcrank, high engine temperature, low lube oil pressure and
overspeed safeties prior to shipment.
Exception No. 2: Where the safety functions are proven to be fail-safe as
demonstrated by monitoring of normal conditions on engine metering
and demonstration that a failed sensor or circuit will not cause shut‐
down of the engine, further testing of the safeties is not required.
7.13.4.6 Items (1) through (4) shall be made available to the
authority having jurisdiction at the time of the acceptance test:
(1)
(2)
(3)
(4)
Evidence of the prototype test as specified in 5.2.1.2 (for
Level 1 systems)
A certified analysis as specified in 5.6.10.2
A letter of compliance as specified in 5.6.10.5
A manufacturer’s certification of a rated load test at rated
power factor with the ambient temperature, altitude, and
fuel grade recorded
Chapter 8 Routine Maintenance and Operational Testing
the time specified for the type and for the time duration speci‐
fied for the class.
8.3.2 A routine maintenance and operational testing program
shall be initiated immediately after the EPSS has passed accept‐
ance tests or after completion of repairs that impact the opera‐
tional reliability of the system.
8.3.2.1 The operational test shall be initiated at an ATS and
shall include testing of each EPSS component on which main‐
tenance or repair has been performed, including the transfer
of each automatic and manual transfer switch to the alternate
power source, for a period of not less than 30 minutes under
operating temperature.
8.3.3 A written schedule for routine maintenance and opera‐
tional testing of the EPSS shall be established.
8.3.4* Transfer switches shall be subjected to a maintenance
and testing program that includes all of the following opera‐
tions:
8.1* General.
(1)
(2)
8.1.1 The routine maintenance and operational testing
program shall be based on all of the following:
(3)
(4)
(1)
(2)
(3)
(4)
8.3.5* Paralleling gear shall be subject to an inspection, test‐
ing, and maintenance program that includes all of the follow‐
ing operations:
Manufacturer’s recommendations
Instruction manuals
Minimum requirements of this chapter
The authority having jurisdiction
8.1.2 Consideration shall be given to temporarily providing a
portable or alternate source whenever the emergency genera‐
tor is out of service and the criteria set forth in Section 4.3
cannot be met.
8.2* Manuals, Special Tools, and Spare Parts.
8.2.1 At least two sets of instruction manuals for all major
components of the EPSS shall be supplied by the manufac‐
turer(s) of the EPSS and shall contain the following:
(1)
(2)
(3)
(4)
(5)
A detailed explanation of the operation of the system
Instructions for routine maintenance
Detailed instructions for repair of the EPS and other
major components of the EPSS
An illustrated parts list and part numbers
Illustrated and schematic drawings of electrical wiring
systems, including operating and safety devices, control
panels, instrumentation, and annunciators
8.2.2 For Level 1 systems, instruction manuals shall be kept in
a secure, convenient location, one set near the equipment, and
the other set in a separate location.
8.2.3 Special tools and testing devices necessary for routine
maintenance shall be available for use when needed.
8.2.4 Replacement for parts identified by experience as high
mortality items shall be maintained in a secure location(s) on
the premises.
8.2.4.1 Consideration shall be given to stocking spare parts as
recommended by the manufacturer.
8.3 Maintenance and Operational Testing.
8.3.1* The EPSS shall be maintained to ensure to a reasona‐
ble degree that the system is capable of supplying service within
2019 Edition
(1)
(2)
(3)
(4)
(5)
Checking of connections
Inspection or testing for evidence of overheating and
excessive contact erosion
Removal of dust and dirt
Replacement of contacts when required
Checking connections
Inspecting or testing for evidence of overheating and
excessive contact erosion
Removing dust and dirt
Replacing contacts when required
Verifying that the system controls will operate as intended
8.3.6* Storage batteries, including electrolyte levels or battery
voltage, used in connection with systems shall be inspected
weekly and maintained in full compliance with manufacturer's
specifications.
8.3.6.1 Maintenance of lead-acid batteries shall include the
monthly testing and recording of electrolyte specific gravity.
Battery conductance testing shall be permitted in lieu of the
testing of specific gravity when applicable or warranted.
8.3.6.2 Defective batteries shall be replaced immediately upon
discovery of defects.
8.3.7 A fuel quality test shall be performed at least annually
using appropriate ASTM standards or the manufacturer’s
recommendations.
8.4 Operational Inspection and Testing.
8.4.1* EPSSs, including all appurtenant components, shall be
inspected weekly and exercised under load at least monthly.
8.4.1.1 If the generator set is used for standby power or for
peak load shaving, such use shall be recorded and shall be
permitted to be substituted for scheduled operations and test‐
ing of the generator set, providing the same record as required
by 8.3.4.
8.4.2* Generator sets in service shall be exercised at least once
monthly, for a minimum of 30 minutes, using one of the follow‐
ing methods:
ROUTINE MAINTENANCE AND OPERATIONAL TESTING
(1)
(2)
Loading that maintains the minimum exhaust gas
temperatures as recommended by the manufacturer
Under operating temperature conditions and at not less
than 30 percent of the EPS standby nameplate kW rating
8.4.2.1 The date and time of day for required testing shall be
decided by the owner, based on facility operations.
8.4.2.2 Equivalent loads used for testing shall be automatically
replaced with the emergency loads in case of failure of the
primary source.
8.4.2.3* Diesel-powered EPS installations that do not meet the
requirements of 8.4.2 shall be exercised monthly with the avail‐
able EPSS load and shall be exercised annually with supple‐
mental loads at not less than 50 percent of the EPS nameplate
kW rating for 30 continuous minutes and at not less than
75 percent of the EPS nameplate kW rating for 1 continuous
hour for a total test duration of not less than 1.5 continuous
hours.
8.4.2.4 The date and time of day for required testing shall be
decided by the owner, based on facility operations.
8.4.2.4.1 Equivalent loads used for testing shall be automati‐
cally replaced with the emergency loads in case of failure of the
primary source.
110-21
8.4.7.1 Circuit breakers rated in excess of 600 volts for Level 1
system usage shall be exercised every 6 months and shall be
tested under simulated overload conditions every 2 years.
8.4.8 EPSS components shall be maintained and tested by
qualified person(s).
8.4.9* Level 1 EPSS shall be tested at least once within every
36 months.
8.4.9.1 Level 1 EPSS shall be tested continuously for the dura‐
tion of its assigned class (see Section 4.2).
8.4.9.2 Where the assigned class is greater than 4 hours, it
shall be permitted to terminate the test after 4 continuous
hours.
8.4.9.3 The test shall be initiated by operating at least one
transfer switch test function and then by operating the test
function of all remaining ATSs, or initiated by opening all
switches or breakers supplying normal power to all ATSs that
are part of the EPSS being tested.
8.4.9.4 A power interruption to non-EPSS loads shall not be
required.
8.4.9.5 The minimum load for this test shall be as specified in
8.4.9.5.1, 8.4.9.5.2, or 8.4.9.5.3.
8.4.3 The EPS test shall be initiated by simulating a power
outage using the test switch(es) on the ATSs or by opening a
normal breaker. Opening a normal breaker shall not be
required.
8.4.9.5.1* For a diesel-powered EPS, loading shall be not less
than 30 percent of the nameplate kW rating of the EPS. A
supplemental load bank shall be permitted to be used to meet
or exceed the 30 percent requirement.
8.4.3.1* Where multiple ATSs are used as part of an EPSS, the
monthly test initiating ATSs shall be rotated to verify the start‐
ing function on each ATS.
8.4.9.5.2 For a diesel-powered EPS, loading shall be that
which maintains the minimum exhaust gas temperatures as
recommended by the manufacturer.
8.4.4 Load tests of generator sets shall include complete cold
starts.
8.4.9.5.3 For spark-ignited EPSs, loading shall be the available
EPSS load.
8.4.5 Time delays shall be set as follows:
8.4.9.6 The test required in 8.4.9 shall be permitted to be
combined with one of the monthly tests required by 8.4.2 and
one of the annual tests required by 8.4.2.3 as a single test.
(1)
(2)
(3)
(4)
Time delay on start:
(a) 1 second minimum
(b) 0.5 second minimum for gas turbine units
Time delay on transfer to emergency: no minimum
required
Time delay on restoration to normal: 5 minutes mini‐
mum
Time delay on shutdown: 5 minutes minimum
8.4.9.7* Where the test required in 8.4.9 is combined with the
annual load bank test, the first portion of the test shall be at
not less than the minimum loading required by 8.4.9.5, the last
hour shall be at not less than 75 percent of the nameplate kW
rating of the EPS, and the duration of the test shall be in
accordance with 8.4.9.1 and 8.4.9.2.
8.4.6 Transfer switches shall be operated monthly.
8.5 Records.
8.4.6.1* The monthly test of a transfer switch shall consist of
electrically operating the transfer switch from the primary posi‐
tion to the alternate position and then a return to the primary
position.
8.5.1 Records shall be created and maintained for all EPSS
inspections, operational tests, exercising, repairs, and modifica‐
tions.
8.4.6.2 The criteria set forth in Section 4.3 and in Table 4.1(b)
shall not be required during the monthly testing of the EPSS. If
the criteria are not met during the monthly test, a process shall
be provided to annually confirm the capability of the system to
comply with Section 4.3.
8.4.7* EPSS circuit breakers for Level 1 system usage, includ‐
ing main and feed breakers between the EPS and the transfer
switch load terminals, shall be exercised annually with the EPS
in the “off” position.
8.5.2 Records required in 8.5.1 shall be made available to the
authority having jurisdiction on request.
8.5.3 The record shall include the following:
(1)
(2)
(3)
(4)
The date of the maintenance report
Identification of the servicing personnel
Notation of any unsatisfactory condition and the correc‐
tive action taken, including parts replaced
Testing of any repair in the time recommended by the
manufacturer
8.5.4 Records shall be retained for a period of time defined by
the facility management or by the authority having jurisdiction.
2019 Edition
110-22
EMERGENCY AND STANDBY POWER SYSTEMS
Annex A Explanatory Material
(8)
Lube system, if required
Annex A is not a part of the requirements of this NFPA document but is
included for informational purposes only. This annex contains explan‐
atory material, numbered to correspond with the applicable text para‐
graphs.
The EPS includes all the related electrical and mechanical
components of the proper size and/or capacity required for
the generation of the required electrical power at the EPS
output terminals.
A.1.1.4 See NFPA 111.
A.3.3.4 Emergency Power Supply System (EPSS). Where
multiple generators are connected together on a common bus,
the common bus is considered to be the system source. See
Annex B for diagrams of typical systems.
A.1.1.5(3) See Chapter 4.
A.1.4.1 Assignment of degree of reliability of the recognized
EPSS, or equivalency of other methods, depends on the careful
evaluation of the variables at each particular installation. One
source of information on quantitative methods for assessing
power system reliability is ANSI/IEEE 493, Recommended Practice
for the Design of Reliable Industrial and Commercial Power Systems.
A.3.2.1 Approved. The National Fire Protection Association
does not approve, inspect, or certify any installations, proce‐
dures, equipment, or materials; nor does it approve or evaluate
testing laboratories. In determining the acceptability of installa‐
tions, procedures, equipment, or materials, the authority
having jurisdiction may base acceptance on compliance with
NFPA or other appropriate standards. In the absence of such
standards, said authority may require evidence of proper instal‐
lation, procedure, or use. The authority having jurisdiction
may also refer to the listings or labeling practices of an organi‐
zation that is concerned with product evaluations and is thus in
a position to determine compliance with appropriate standards
for the current production of listed items.
A.3.2.2 Authority Having Jurisdiction (AHJ). The phrase
“authority having jurisdiction,” or its acronym AHJ, is used in
NFPA documents in a broad manner, since jurisdictions and
approval agencies vary, as do their responsibilities. Where
public safety is primary, the authority having jurisdiction may
be a federal, state, local, or other regional department or indi‐
vidual such as a fire chief; fire marshal; chief of a fire preven‐
tion bureau, labor department, or health department; building
official; electrical inspector; or others having statutory author‐
ity. For insurance purposes, an insurance inspection depart‐
ment, rating bureau, or other insurance company
representative may be the authority having jurisdiction. In
many circumstances, the property owner or his or her designa‐
ted agent assumes the role of the authority having jurisdiction;
at government installations, the commanding officer or depart‐
mental official may be the authority having jurisdiction.
A.3.2.4 Listed. The means for identifying listed equipment
may vary for each organization concerned with product evalua‐
tion; some organizations do not recognize equipment as listed
unless it is also labeled. The authority having jurisdiction
should utilize the system employed by the listing organization
to identify a listed product.
A.3.3.1 Battery Certification. One such certifier of batteries is
the American Association of Battery Manufacturers.
A.3.3.3 Emergency Power Supply (EPS). For rotary energy
converters, components of an EPS include the following:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
Prime mover
Cooling system
Generator
Excitation system
Starting system
Control system
Fuel system
2019 Edition
A.3.3.9.1 Valve-Regulated (VRLA). In VRLA batteries, the
liquid electrolyte in the cells is immobilized in an absorptive
glass mat (AGM cells or batteries) or by the addition of a
gelling agent (gel cells or gelled batteries).
A.3.3.9.2 Vented (Flooded). Flooded lead-acid batteries might
have a provision for the user to add water to the cell and are
equipped with a flame-arresting vent that permits the escape of
hydrogen and oxygen gas from the cell in a diffused manner
such that a spark, or other ignition source, outside the cell will
not ignite the gases inside the cell.
A.4.1 This standard specifies requirements for the EPSS as a
complete functioning system in terms of types, classes, and
levels. It is not the intent of this standard to recommend the
EPSS most suitable for any given application. The terms emer‐
gency power supply systems and standby power supply systems as used
in this standard include, but are not limited to, such terms as
the following:
(1)
(2)
(3)
(4)
Alternate power systems
Standby power systems
Legally required standby systems
Alternate power sources
Since this standard specifies the installation, performance,
maintenance, and test requirements in terms of types, classes,
and levels, any of these terms might be appropriate for describ‐
ing the application or use, depending on the need and the
preference of the parties involved.
A.4.2 Selection of the class of the EPSS should take into
account past outage records and fuel delivery problems due to
weather, shortages, and other geographic and environmental
conditions. Class “X” is a calculated value that usually repre‐
sents between 48 and 96 hours of fuel for a Level 1 facility.
Where the seismic design category is C, D, E, or F, as deter‐
mined in accordance with ASCE/SEI 7, Minimum Design Loads
for Buildings and Other Structures, the EPS supplying a Level 1
EPSS should be capable of a minimum 96 hours of operation
without refueling if it is determined that EPS operation is
necessary for this period.
A.4.4 It is recognized that EPSSs are utilized in many different
locations and for many different purposes. The requirement
for one application might not be appropriate for other applica‐
tions.
A.4.4.1 Typically, Level 1 systems are intended to automatically
supply illumination or power, or both, to critical areas and
equipment in the event of failure of the primary supply or in
the event of danger to elements of a system intended to supply,
distribute, and control power and illumination essential for
safety to human life. Other NFPA codes and standards, such as
NFPA 20, NFPA 99, and NFPA 101, provide specific require‐
ments on where Level 1 systems are required.
ANNEX A
Essential electrical systems can provide power for the follow‐
ing essential functions:
(1)
(2)
(3)
(4)
(5)
(6)
Life safety illumination
Fire detection and alarm systems
Elevators
Fire pumps
Public safety communications systems
Industrial processes where current interruption would
produce serious life safety or health hazards
Essential ventilating and smoke removal systems
110-23
(1)
(2)
(3)
Motor-generator/engine
Motor-generator/flywheel
Steam turbine
Connection to the primary power source ahead of the
primary source main service disconnect and a separate service
should be excluded as a sole source of EPS.
A.4.4.2 Typically, Level 2 systems are intended to supply power
automatically to selected loads (other than those classed as
emergency systems) in the event of failure of the primary
source.
A.5.4 It is recognized that in some installations, part or all of
the output of the EPS might be used for peak shaving or part of
the output might be used for driving nonessential loads during
loss of the primary power source. Load shedding of these loads
when the output of the energy converter is needed is one way
of meeting the requirements of Section 5.4. The load should
be reviewed to ascertain that load growth has not exceeded
EPS capability.
Level 2 systems typically are installed to serve loads, such as
the following, that, when stopped due to any interruption of
the primary electrical supply, could create hazards or hamper
rescue or fire-fighting operations:
A.5.5.2 The low-fuel alarm point for liquid-fueled engines is
defined as the point when the main fuel tank contains insuffi‐
cient fuel to meet the required full load operating hours and is
the point at which this condition is signaled.
(1)
(2)
(3)
(4)
(5)
(6)
A.5.5.3 Consideration should be given to sizing tanks in order
to meet minimum fuel supplier delivery requirements, particu‐
larly for small tanks. Consideration also should be given to
oversizing tanks. More important, biodiesel blends up to B5
(ASTM D975, Standard Specification for Diesel Fuel Oils) have
much shorter shelf lives than conventional diesel fuel [ultralow sulfur diesel (ULSD)] and can accelerate degradation
processes, endangering the entire diesel fuel supply. Where
fuel is stored for extended periods of time (e.g., more than
12 months), it is recommended that fuels be periodically
pumped out and used in other services and replaced with fresh
fuel. Prudent disaster management could require much larger
on-site temporary or permanent fuel storage, and several
moderate-sized tanks can be preferable to a single very large
tank.
(7)
Heating and refrigeration systems
Communications systems
Ventilation and smoke removal systems
Sewage disposal
Lighting
Industrial processes
A.4.4.3 The intent is not to prohibit the use of portable or
alternate equipment whenever the permanent EPSS is out of
service. (See 8.1.2.)
A.4.4.4 It is important to recognize that an EPSS might react
substantially differently from commercial power during transi‐
ent and short circuit conditions due to the relatively small
capacities of the EPSS compared to the primary commercial
power source. [See ANSI/NEMA C 84.1, Standard for Electric Power
Systems and Equipment — Voltage Ratings (60 hertz).]
A.5.1.1 Examples of probability of interruption could include
the following: earthquake, flood damage, or a demonstrated
utility unreliability.
A.5.1.1(1) The grade of diesel fuel selected for use in a prime
mover should be based on recommendations from the diesel
engine manufacturer and ASTM D975, Standard Specification for
Diesel Fuel Oils. The purchaser of fuel for the prime mover
should specify a diesel fuel that does not contain biodiesel,
which can accelerate the degradation of the diesel fuel if stored
longer than 6 months. If diesel fuel is stored outside for longterm storage, it can be necessary to use a winter or arctic grade
of diesel fuel or to take precautions such as insulating and heattracing fuel tanks and lines to ensure that fuel will flow to the
prime mover under the coldest possible conditions.
A.5.1.1(2) ASTM D1835, Standard Specification for Liquified
Petroleum (LP) Gases, is a recognized standard covering LP-Gas.
A.5.1.1(3) ASTM does not have a standard specification for
natural or synthetic gas. Industry generally uses pipeline speci‐
fications for natural gas quality.
A.5.1.3 On-site energy conversion is not restricted to rotatingtype generating systems. Other types of continuous energy
conversion systems can be used, including fuel-cell systems.
A.5.6.4.2 See Figure A.5.6.4.2 for a diagram of cranking cycles.
A.5.6.4.3 A battery unit is one or more batteries or a group of
cells, a series, or a parallel series connected to provide the
required battery unit voltage and capacity.
A.5.6.4.4 Cold-cranking amperes, or cranking performance,
are the number of amperes a fully charged battery at −17.8°C
(0°F) can continuously deliver for 30 seconds while maintain‐
ing 1.2 V per cell.
Cranking limit time-out
Crank cycle
15 sec
15 sec
15 sec
15 sec
15 sec
15 sec
Crank
Rest
Crank
Rest
Crank
Rest
FIGURE A.5.6.4.2
Diagram of Cranking Cycles.
A.5.2.2 The following devices are typical of energy converters
and energy sources that should be reviewed carefully as part of
Level 1 EPSs:
2019 Edition
110-24
EMERGENCY AND STANDBY POWER SYSTEMS
A.5.6.4.5.1 It is recommended that lead-acid starting batteries
be replaced every 24 to 30 months.
A.5.6.4.6 It is intended that the battery charger be factorybuilt, adjusted, and approved for the specific type, construc‐
tion, and capacity of the battery.
A.5.6.6 The minimum “remote alarm annunciation” is to alert
personnel at a constantly attended station somewhere on the
site when the facility is in use as a Level 1 system. If the site is
not continuously occupied, “network remote” should allow
people at another site to know the operating status of the
equipment.
The preferred method of remote annunciation is to notify
personnel both somewhere on the site and at other locations
via a network such as LAN, WAN, or Internet, including the
ability to initiate auto-dial and send predefined text messages.
A.5.6.7.4 Adding remote parasitic equipment loads into the
overall load to be supplied by the EPS is a factor that should be
included in the overall EPSS design.
A.5.6.9.1 See ANSI/NEMA MG 1, Standard for Motors and
Generators, and ANSI/NEMA MG 2, Safety Standard and Guide for
Selection, Installation and Use of Electric Motors and Generators.
A.5.6.10.3 Where unusual vibration conditions are anticipa‐
ted, adequate isolation treatment should be supplied.
A.6.2.4 Authorized personnel should be available and familiar
with manual operation of the transfer switch and should be
capable of determining the adequacy of the alternate source of
power prior to manual transfer.
A.6.2.5 For most applications, a nominal delay of 1 second is
adequate. The time delay should be short enough so that the
generator can start and be on line within the time specified for
the type classification.
A.6.2.8 It is recommended that the timer for delay on retrans‐
fer to the primary source be set for 30 minutes. The 30-minute
recommendation is to establish a “normalized” engine temper‐
ature when it is beneficial for the engine. NFPA 70 establishes a
minimum time requirement of 15 minutes.
A.6.2.13 For maintenance purposes, consideration should be
given to a transfer switch counter.
A.6.2.15 ATSs can be provided with accessory controls that
provide a signal to operate remote motor controls that discon‐
nect motors prior to transfer and to reconnect them after trans‐
fer when the residual voltage has been substantially reduced.
Another method is to provide in-phase monitors within the
ATS in order to prevent retransfer to the primary source until
both sources are nearly synchronized. A third method is to use
a programmed neutral position transfer switch.
A.6.1.1 Electrical switching is electrical equipment or devices
used to do any or all of the following:
A.6.2.16 Standards for nonautomatic transfer switches are
similar to those for ATSs, as defined in 3.3.12.1 and 3.3.12.3,
with the omission of automatic controls.
(1)
A.6.4.3 See Section 700.6 of NFPA 70.
(2)
(3)
Transfer connected electrical loads from one power
source to another
Perform load-switching functions
Bypass, isolate, and test the transfer switch
A.6.1.2 Electrical protection equipment is sensing and over‐
current protective devices used to protect against damage due
to fault or overload to conductors and equipment connected to
the output of the emergency energy source, up to and includ‐
ing the load terminals of the transfer switch(es).
A.6.1.6 See Section 695.10 of NFPA 70 and Section 10.8 of
NFPA 20, for listing and installation requirements for transfer
switches used with fire pumps.
A.6.2.1 For most applications in this standard, the automatic
transfer switch (ATS) is used to transfer a load from a primary
source of supply to an engine generator set.
An ATS might include circuit breakers, contactors, switches,
or vacuum and solid-state power devices operating in conjunc‐
tion with automatic-sensing and logic devices to perform the
defined function.
A.6.2.2.1 Where special loads require more rapid detection of
power loss, underfrequency monitoring also might be pro‐
vided. Upon frequency decay below the lower limit necessary
for proper operation of the loads, the transfer switch should
automatically initiate transfer to the alternate source. (See
A.6.2.15.)
A.6.2.2.1(2) See 6.2.5 and 6.2.7.
A.6.2.3 Certain installations might use automatic transfer
switch equipment with momentary closed transition or softloading capabilities. This equipment should be applied with
the approval of the local utility and authority having jurisdic‐
tion.
2019 Edition
A.6.4.4 Consideration should be given to the effect that load
interruption could have on the load during maintenance and
service of the transfer switch.
A.6.5.1 It is important that the various overcurrent devices be
coordinated, as far as practicable, to isolate faulted circuits and
to protect against cascading operation on short circuit faults. In
many systems, however, full coordination is not practicable
without using equipment that could be prohibitively costly or
undesirable for other reasons. Primary consideration also
should be given to prevent overloading of equipment by limit‐
ing the possibilities of large current inrushes due to instanta‐
neous reestablishment of connections to heavy loads.
A.6.5.3 See 9.6.5 of NFPA 20.
A.7.1.1 The performance of the EPS and the EPSS is depend‐
ent on many factors, one of which is correct initial installation,
primarily as the installation relates to the location and environ‐
mental conditions. Although this standard is not intended to
serve as a design standard for EPSS installation and environ‐
mental considerations, certain minimum standards are recog‐
nized as essential for successful startup and performance, safe
operation, and utilization of the EPSS where required.
A.7.1.2 The environmental conditions to be considered in the
EPSS design should include, but not be limited to, heating,
ventilating, and air-conditioning systems; protection from
floods, fire, vandalism, wind, earthquakes, lightning, and other
similar or applicable environmental conditions common to
geographic locations; and other factors affecting the location
of the EPSS equipment.
The probability and frequency of power failures that do or
can occur as a result of lightning, wind, and rain produced by
ANNEX A
thunderstorms, hurricanes, tornadoes, and similar weather
conditions associated with the user's geographic location
should be considered.
A.7.2.3 The intent of this requirement is to provide maximum
fire protection to the most critical, high energy systems.
Consideration should be given to the potential fire hazard
when locating Level 2 EPSS equipment in the normal electrical
service room, or to Level 1 systems below 1000 amperes and
150 volts to ground.
A.7.2.4 EPSS equipment should be located above known
previous flooding elevations where possible.
A.7.2.5 When installing the EPSS equipment and related
auxiliaries, environmental considerations should be given,
particularly with regard to the installation of the fuel tanks (see
A.7.9.1.2) and exhaust lines, or the EPS building, or both.
To protect against disruption of power in the facility, it is
recommended that the transfer switch be located as close to
the load as possible. The following are examples of external
influences:
(1)
Natural conditions such as the following:
(2)
(a) Storms
(b) Floods
(c) Earthquakes
(d) Tornadoes
(e) Hurricanes
(f) Lightning
(g) Ice storms
(h) Wind
(i) Fire
Human-caused conditions such as the following:
(3)
(a) Vandalism
(b) Sabotage
(c) Other similar occurrences
Material and equipment failures
For natural conditions, EPSS design should consider the
“100-year storm” flooding level or the flooding level predicted
by the Sea, Lake, and Overland Surges from Hurricanes
(SLOSH) models for a Category 4 hurricane. For further infor‐
mation refer to FEMA 543 and FEMA 577, both dated August
11, 2013.
A.7.3.3 Where units housed outdoors are used, it is recom‐
mended that a flashlight or battery-powered light with a flexi‐
ble cord be maintained in the housing.
A.7.5 Generally, integral rubber vibration isolators are used on
the rotating energy converters, and spring-type or pad-type
isolators are used on the larger energy converter units. In some
cases, high deflection spring-type isolators should be used
where a high degree of vibration attenuation is required. The
EPS manufacturer should be consulted during consideration of
the specific type of vibration control. Inertia bases should be
considered where unusual vibration conditions are anticipated.
A.7.6 Generally, exhaust noises can be attenuated by using the
proper mufflers. The mufflers used should be in accordance
with the EPS manufacturer's recommendations. Depending on
the degree of silencing required, the muffler should be rated
accordingly for “commercial,” “semicritical,” and “critical”
(high degree of silencing) service. To attenuate other noises,
line-of-sight barriers having acoustical treatment or total acous‐
110-25
tical enclosures can be used. The EPS should be installed away
from critical areas.
A.7.7.1 During operation, EPS and related equipment reject
considerable heat that needs to be removed by proper ventila‐
tion or air-cooling. In some cases, outdoor installations rely on
natural air circulation, but enclosed installations need properly
sized, properly positioned ventilation facilities, to prevent recir‐
culation of cooling air. The optimum position of air-supply
louvers and radiator air discharge is on opposite walls, both to
the outdoors.
A.7.7.2.1 The ventilation calculation for an EPS should
consider the following:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
Radiator airflow (when installed in the EPS room)
Combustion airflow consumed by the engine
Maximum potential ambient temperature of air entering
the EPS room for ventilation
Radiated heat load from the EPS
Radiated heat load from EPS exhaust system whether it is
insulated or not insulated
Other heat loads in the room
Maximum allowed airflow pressure drop through the
ventilation supply into the room and through the ventila‐
tion discharged from the radiator
A.7.9.1.1 Cleaning and purging of flammable gas piping
systems should be in accordance with NFPA 56.
A.7.9.1.2 To optimize the long-term storage of fuels for prime
movers, the fuel tanks should be kept cool and dry, and the
tank as full as possible. Tanks that are subject to temperature
variations can experience accelerated fuel degradation, espe‐
cially if the tanks are outside and above ground or close to an
extreme heat source if stored inside a structure. The more
constant and cooler the tank temperatures, the less likely
temperature-related fuel degradation will occur. Tank ullage
(air space) should be kept to a minimum. Excess air space
allows for warm, humid air to enter the tank and condense
moisture during the cool evening. Also, prolonged exposure to
ambient air, which is 20 percent oxygen, can facilitate oxidative
degradation of the fuel. Fuel storage tanks should be kept as
dry as possible and have provisions for water drainage on a
regular basis. The presence of water can lead to microbiologi‐
cal contamination and growth, which in turn can lead to
general or pitting corrosion of steel tanks and components,
possibly resulting in filter plugging, operational issues, or a
hydrocarbon release to the environment. Regularly scheduled
surveillance of the fuel allows the operator(s) to evaluate the
condition of the fuel and make important decisions regarding
the quality of the fuel dedicated to reliable operation of the
prime mover. Fuel maintenance and testing should begin the
day of installation and first fill in order to establish a bench‐
mark guideline for future comparison. Laboratory testing serv‐
ices should always be sought from a qualified or certified
petroleum laboratory.
A.7.9.3.1 Fuel lines containing copper, copper-containing
alloys, and zinc (including galvanized piping or containers)
should be avoided. Copper can promote fuel degradation and
can produce mercaptide gels. Zinc coatings can react with
water or organic acids in the fuel to form gels that rapidly plug
filters.
A.7.9.6 See NFPA 37, NFPA 54, and NFPA 58.
2019 Edition
110-26
EMERGENCY AND STANDBY POWER SYSTEMS
A.7.9.7 Valving for natural gas–fueled prime movers should be
configured so that the gas supply to the prime mover cannot be
inadvertently or intentionally shut off by anyone other than
qualified personnel such as the gas supplier. If valves are placed
in an isolated area, a secure area or locking the valve(s) open is
recommended.
A.7.10.3 Consideration should also be given to utilizing damp‐
ening supports where it is necessary to reduce exhaust noise
vibration transmission.
A.7.11.2 If a fire suppression system is used in EPS rooms or
separate buildings housing EPS equipment, consideration
should be given to preaction-type suppression systems.
A.7.11.5 Consideration should be given to the location of the
EPS equipment, both as it relates to the building structure and
to the effects of an earthquake.
All emergency power equipment support or subsupport
systems should be designed and constructed so that they can
withstand static or anticipated seismic forces, or both, in any
direction, with the minimum force value used being equal to
the equipment weight.
Bolts, anchors, hangers, braces, and other restraining devi‐
ces should be provided to limit earthquake-generated differen‐
tial movements between the EPS nonstructural equipment and
the building structure. However, the degree of isolation
required for vibration and acoustical control of the EPS equip‐
ment and other equipment should be maintained.
Suspended items such as piping, conduit, ducts, and other
auxiliary equipment related to the EPSS should be braced in
two directions to resist swaying and excessive movement in
earthquake risk areas.
Battery racks for EPS equipment and electrical items or rela‐
ted auxiliaries, or both, should be designed to resist internal
damage and damage at the equipment supports resulting from
earthquake-generated motion. Battery racks should be capable
of withstanding seismic forces equal to the supported weight in
any direction. Batteries should be restrained to their support to
prevent vibration damage, and electrical interconnections
should be provided with adequate slack to accommodate all
relative deflections.
Transfer switch enclosures should be mounted so that their
anchors and support structures can withstand static forces
equal to the anticipated seismic shock in any direction.
Transfer switch components should be of the type that resists
malfunction during dynamic excitation and should be
designed to resist the anticipated seismic shock.
Where possible, EPS equipment and associated cooling
systems and controls should be mounted on a single frame.
The frame, in turn, should be rigidly attached to its foundation
so that its anchorage can withstand static forces equal to the
equipment weight in any direction. Where engine generator
sets and associated cooling systems' controls cannot be moun‐
ted as an integral unit, each should be secured to meet the
floating requirements previously described. Equipment not
using the preferred rigid mounting should have vibration isola‐
tors with restraints capable of withstanding static forces equal
to twice the weight of the supported equipment in any direc‐
tion. In addition, interconnecting power, fuel, and cooling
lines should be provided with adequate flexibility to allow
maximum anticipated excursions without damage.
2019 Edition
Appendages to the EPS equipment, such as day tanks,
should be mounted to withstand static forces equal to the
anticipated seismic shock in any direction.
A.7.11.6 Seismic shock should be simulated at the factory or
in a testing laboratory on a prototype unit. Simulation should
consist of a test(s) approximating actual time-history records of
known seismic shocks applied to the equipment under test.
Subassemblies of the total equipment could be tested sepa‐
rately where it is neither practical nor feasible to test the
complete unit.
A.7.13.4.1.1 Cold start is typical standby condition under
normal ambient conditions with coolant heaters functioning
normally.
A.7.13.4.1.2 Cold start is typical standby condition under
normal ambient conditions with coolant heaters functioning
normally.
A.7.13.4.1.4(6) Verification of the engine start function can be
accomplished by actual starting of the engine or by testing of
the ATS start circuit.
A.7.13.4.3 Connection of the load bank (or a portable genera‐
tor) is facilitated by providing permanently installed equip‐
ment or connection points such as spare circuit breakers or
switches.
The generator set manufacturer should be consulted where
the nameplate data do not indicate rating type. There is a
difference between prime and standby ratings. For example,
there are usually two kW nameplate ratings found on most
engine-driven generators: “standby” and “prime.” There can be
a significant difference between the resulting kW figures when
calculating 30 percent of nameplate — for example, a 100 kW
standby generator is normally considered an 80 kW set for
prime power: 100 kW × 30% = 30 kW, but 80 kW × 30% =
24 kW. A permanent record of the rating should be maintained
and readily available.
A.7.13.4.3.1 The generator set manufacturer should be
consulted where the nameplate data do not indicate rating
type. There is a difference between prime and standby ratings.
For example, there are usually two kW nameplate ratings found
on most engine-driven generators: “standby” and “prime.”
There can be a significant difference between the resulting kW
figures when calculating 30 percent of nameplate — for exam‐
ple, a 100 kW standby generator is normally considered an
80 kW set for prime power: 100 kW × 30% = 30 kW, but 80 kW
× 30% = 24 kW. A permanent record of the rating should be
maintained and readily available.
A.8.1 The continuing reliability and integrity of the EPSS are
dependent on an established program of routine maintenance
and operational testing. For more detailed information on
electrical equipment maintenance, refer to NFPA 70B.
A.8.2 Where adequately secured from public access, it is desir‐
able to locate an instruction manual, special tools and testing
devices, and spare parts in the room in which the EPS is loca‐
ted. The articles should be mounted at a convenient location
on a wall and should be enclosed in a metal or other suitable
cabinet. The cabinet should accommodate the instruction
manual on the inside of the door.
A.8.3.1 The suggested maintenance procedure and frequency
should follow those recommended by the manufacturer. In the
ANNEX A
absence of such recommendations, Figure A.8.3.1(a) and
Figure A.8.3.1(b) indicate alternate suggested procedures.
110-27
(2)
(a)
A.8.3.4 Where sealed devices are used, replacement of the
complete device might be necessary. Maintenance should be
performed according to manufacturer’s recommendations. In
the absence of such recommendations, the list given in 8.3.4
suggests minimal procedures.
Transfer switches should be subjected to an annual mainte‐
nance program including (one) major maintenance and
(three) quarterly inspections. Programs should include all of
the following operations. Note: Due to the critical nature of
these devices, permission should be gained to perform these
tasks since some of the following recommendations could
cause disruption of power to the load. The following tasks
should be carefully reviewed with facility management person‐
nel to ensure agreement and plan for contingencies.
Major Maintenance
(1)
Check connections.
A thermographic or temperature scan should be
done prior to this visit, while the ATS is under
normal (peak) load. This thermographic scan
should be repeated during the EPSS load test.
Results should be available to the maintenance
provider so that suspect conditions can be
addressed during this activity.
(b) With power connected to the normal source, mea‐
sure and record millivolt drop levels across each
pole. Note: Any reading that is greater than
25 percent of the average of all poles should be
carefully inspected when the ATS is de-energized.
(c) With power connected to the emergency source,
measure and record millivolt drop levels across each
pole. Note: Any reading that is greater than
25 percent of the average of all poles should be
carefully inspected when the ATS is de-energized.
(d) If the ATS is equipped with a bypass isolation
feature, operate the bypass to the connected source
(emergency or normal) and repeat the steps in (a),
(b), and (c). Levels should drop to approximately
50 percent of initial levels and be uniform relative
to initial readings. This step verifies that the bypass
feature is properly connected and that the con‐
nected load will not be affected when the automatic
portion is isolated for maintenance.
(e) With power secured and both the emergency and
normal sources properly locked out and tagged out,
measure the micro-ohm resistance levels across the
following connection points:
(a)
i.
ii.
iii.
iv.
v.
vi.
Emergency source cabling lug to bus
Normal source cabling lug to bus
Load cabling lug to bus
Neutral cabling lug to bus
Load connected to normal across each pole
Load connected to emergency across each
pole
Note: If the ATS is equipped with an isolation bypass and
the bypass remains energized, perform these tests on the
isolated transfer switch unit only. DO NOT APPLY DIGI‐
TAL LOW RESISTANCE OHMMETER (DLRO) TO
ENERGIZED CIRCUITS. Any value greater than
20 percent of the average value of all similar type connec‐
tions requires further investigation.
Inspect or test for evidence of overheating or excessive
contact corrosion.
(3)
With power from both sources secured and properly
locked out and tagged out, remove all protective
pole covers and arc chutes.
(b) Carefully inspect main contacts and other currentcarrying parts for signs of corrosion or overheating.
Note: Observation should correlate with previous
results (i.e., thermographic or temperature
evidence of higher than normal temperatures or
heat migration, abnormal millivolt drop readings as
previously noted, or abnormal micro-ohm (DLRO)
readings as previously noted).
(c) Carefully inspect insulating materials or standoff
insulators for signs of contamination (dirt, grime,
oil, etc.). The combination of contaminants and
possible introduction of high humidity or moisture
could lead to insulation breakdown and subsequent
destructive faults. Clean contaminated surfaces with
a solvent approved for this purpose.
(d) Inspect control connection, plugs, and harnesses
for signs of corrosion, heat, contamination, and so
forth.
(e) Using a vacuum, remove all dust and debris from
the ATS cabinet, transfer switch mechanism, bus,
and so forth. Note: Never use compressed air to
blow out dust. Doing so can blow dust and debris
into controls and the transfer switch mechanism.
(f) Inspect cabinets for proper sealing. Open conduit
knockouts or other penetrations should be properly
sealed to prevent the introduction of dust, mois‐
ture, or other alien matter. Enclosures installed
outside should be inspected for proper seal and
appropriate gasketing. Ensure that enclosure door
securing devices are intact and properly secured.
(g) Replace and secure all protective pole covers and
chutes. Remove lockout devices and resupply
normal power. If the ATS is of the bypass isolation
type, reconnect the transfer switch mechanism.
Observe proper manufacturer’s procedures.
Verify control and feature setpoints and operation.
(a)
Measure and record the following data and
setpoints:
i.
Normal source voltage phase to phase, phase
to ground, and phase to neutral
ii.
Engine start time (from crank start to source
available light or relay pickup)
iii. Emergency source voltage phase to phase,
phase to ground, and phase to neutral
iv.
Load current each phase
v.
Momentary override normal deviation where
provided
vi. Transfer time delay where provided
vii. Return to normal source time delay where
provided
viii. Engine cooldown where provided
(b) If the connection is to a multiple-source EPS, verify
the load priority of the ATS being tested and
confirm this is correct given the criticality of the
connected load.
(c) Verify proper operation of all indicator lights and
meters and controls.
(d) Return ATS to normal service.
2019 Edition
110-28
EMERGENCY AND STANDBY POWER SYSTEMS
EPSS Maintenance Schedule
Procedure
Frequency
X — Action
R — Replace, if needed
Component (as applicable)
Visual
Inspection
Check
Change
Clean
Test
W — Weekly
M — Monthly
Q — Quarterly
S — Semiannually
A — Annually
Nos. indicate hours
Level 1
Level 2
W
M
1. Fuel
(a) Main supply tank level
X
(b) Day tank level
X
W
M
(c) Day tank float switch
X
X
W
Q
(d) Supply or transfer pump operation
X
X
W
Q
(e) Solenoid valve operation
X
X
W
Q
X
Q
Q
X
W
Q
W
M
A
A
X
(f) Strainer, filter, dirt leg, or
combination
(g) Water in system
(h) Flexible hose and connectors
X
X
(i) Tank vents and overflow piping
unobstructed
R
X
X
X
(j) Piping
(k) Gasoline in main tank (when used)
A
A
R
A
A
W
M
R
50 or A
50 or A
R
50 or A
50 or A
W
M
Q
S
W
M
2. Lubrication System
(a) Oil level
X
X
(b) Oil change
(c) Oil filter(s)
(d) Lube oil heater
(e) Crankcase breather
X
X
R
X
3. Cooling System
(a) Level
X
X
(b) Antifreeze protection level
X
(c) Antifreeze
R
(d) Adequate cooling water to heat
exchanger
X
X
(e) Rod out heat exchanger
(f) Adequate fresh air through radiator
X
X
X
(i) Water pump(s)
X
(j) Condition of flexible hoses and
connection
X
(l) Inspect duct work, clean louvers
X
(m) Louver motors and controls
X
W
M
A
A
W
M
A
A
Q
W
Q
W
M
W
M
A
A
A
A
X
W
M
X
W
M
X
X
X
(k) Jacket water heater
A
A
M
(g) Clean exterior of radiator
(h) Fan and alternator belt
S
A
X
X
X
X
4. Exhaust System
X
(a) Leakage
(b) Drain condensate trap
© 2018 National Fire Protection Association
FIGURE A.8.3.1(a)
2019 Edition
Suggested Maintenance Schedule for Emergency Power Supply Systems (EPSSs).
NFPA 110 (p. 1 of 3)
ANNEX A
110-29
EPSS Maintenance Schedule (continued)
Procedure
Frequency
X — Action
R — Replace, if needed
Component (as applicable)
(c) Insulation and fire hazards
Visual
Inspection
Check
Change
Clean
Test
X
(d) Excessive backpressure
X
W — Weekly
M — Monthly
Q — Quarterly
S — Semiannually
A — Annually
Nos. indicate hours
Level 1
Level 2
Q
Q
A
A
(e) Exhaust system hangers and
supports
X
A
A
(f) Flexible exhaust section
X
S
S
X
W
M
X
Q
Q
M
M
M
M
M
M
M
M
W
M
X
A
A
X
Q
S
5. Battery System
(a) Electrolyte level
(b) Terminals clean and tight
X
(c) Remove corrosion, case exterior
clean and dry
X
X
(d) Specific gravity or state of charge
(e) Charger and charge rate
X
X
(f) Equalize charge
X
6. Electrical System
(a) General inspection
X
(b) Tighten control and power wiring
connections
(c) Wire chafing where subject to
movement
X
X
(d) Operation of safeties and alarms
X
X
(e) Boxes, panels, and cabinets
(f) Circuit breakers, fuses
X
X
R
X
X
S
S
S
S
M
A
A
A
A
A
Note: Do not break manufacturer’s
seals or perform internal inspection
on these devices.
(g) Transfer switch main contacts
X
(h) Calibration of voltage-sensing
relays/devices
X
X
X
X
(i) Wire insulation breakdown
a
5/500
3/500b
W
M
7. Prime Mover
(a) General inspection
X
R
(b) Service air cleaner
(c) Governor oil level and linkage
X
X
X
R
(d) Governor oil
(e) Ignition system — plugs, points, coil,
cap, rotor, secondary wire insulation
(f) Choke setting and carburetor
adjustment
X
X
R
X
X
X
S
S
M
M
A
A
A
A
S
S
A
(g) Injector pump and injectors for flow
rate pressure and/or spray pattern
X
A
(h) EPS at minimum of 30% nameplate
rating
X
3/4
© 2018 National Fire Protection Association
FIGURE A.8.3.1(a)
c
c
3/4
NFPA 110 (p. 2 of 3)
Continued
2019 Edition
110-30
EMERGENCY AND STANDBY POWER SYSTEMS
EPSS Maintenance Schedule (continued)
Procedure
Frequency
X — Action
R — Replace, if needed
Component (as applicable)
Visual
Inspection
Check
Change
Clean
Test
W — Weekly
M — Monthly
Q — Quarterly
S — Semiannually
A — Annually
Nos. indicate hours
Level 1
Level 2
X
b
3/500
3/500b
X
3/500b
3/500b
X
S
S
X
A
A
X
(i) Valve clearance
(j) Torque bolts
8. Generator
(a) Brush length, appearance, free to
move in holder
X
(b) Commutator and slip rings
X
(c) Rotor and stator
X
(d) Bearing(s)
X
(e) Bearing grease
X
X
A
A
R
A
A
R
A
A
(f) Exciter
X
X
X
A
A
(g) Voltage regulator
X
X
X
A
A
A
A
(h) Measure and record resistance
readings of windings with insulation
tester (Megger)
X
9. (a) General condition of EPSS, any
unusual condition of vibration,
leakage, noise, temperature, or
deterioration
X
X
W
M
(b) Service room or housing housekeeping
X
X
W
M
W
M
10. Restore system to automatic
operation condition
X
a Every 5 years or 500 hours
b Every 3 years or 500 hours
c Every 3 years for 4 hours
© 2018 National Fire Protection Association
FIGURE A.8.3.1(a)
Continued
Quarterly Inspections
(1)
(2)
NFPA 110 (p. 3 of 3)
Visually inspect the transfer switch control mechanism,
control panel, harnesses, and cable connections for signs
of moisture, corrosion, or heating.
Measure and record the following data and setpoints:
(5)
(a)
(3)
Normal source voltage phase to phase, phase to
ground, and phase to neutral
(b) Engine start time (from crank start to source availa‐
ble light or relay pickup)
(c) Emergency source voltage phase to phase, phase to
ground, and phase to neutral
(d) Load current each phase
(e) Momentary override normal deviation where provi‐
ded
(f) Transfer time delay where provided
(g) Return to normal source time delay where provided
(h) Engine cooldown where provided
If the connection is to a multiple-source EPS, verify the
load priority of the ATS being tested and confirm this is
correct given the criticality of the connected load.
(4)
2019 Edition
(6)
Verify proper operation of all indicator lights and meters
and controls.
Inspect cabinets for proper sealing. Open conduit knock‐
outs or other penetrations should be properly sealed to
prevent the introduction of dust, moisture, or other alien
matter. Enclosures installed outside should be inspected
for proper seal and appropriate gasketing. Ensure that
enclosure door securing devices are intact and properly
secured.
Perform a load test using the test switch if permitted.
Note: This will cause the emergency power source to start
and the ATS to transfer. Be sure to gain permission from
the facility management prior to performing this test.
A.8.3.5 Paralleling switchgear offers many advantages when
testing and exercising. The system exercise period would be
initiated by the automatic transfer switch (ATS) controls, and
once operating, the system could be staged to establish appro‐
priate loading of each EPS.
ANNEX A
EPSS Maintenance Log
Performed by
Service
Frequency
Component
Level 1
Level 2
(a) Main supply tank level
W
M
(b) Day tank level
W
M
(c) Day tank float switch
W
Q
(d) Supply or transfer pump operation
W
Q
(e) Solenoid valve operation
W
Q
(f) Strainer, filter, dirt leg, or
combination
Q
Q
(g) Water in system
W
Q
110-31
Frequency
W — Weekly
M — Monthly
Q — Quarterly
S — Semiannually
A — Annually
Nos. indicate hours
Date
Fill in Appropriate Readings
1. Fuel
(h) Flexible hose and connectors
A
A
(i) Tank vents and overflow piping
unobstructed
A
A
(j) Piping
A
A
(k) Gasoline in main tank (when used)
A
A
W
M
(b) Oil change
50 or A
50 or A
(c) Oil filter(s)
50 or A
50 or A
(d) Lube oil heater
W
M
(e) Crankcase breather
Q
S
2. Lubrication System
(a) Oil level
3. Cooling System
(a) Level
W
M
(b) Antifreeze protection level
S
A
(c) Antifreeze
A
A
(d) Adequate cooling water to heat
exchanger
W
M
(e) Rod out heat exchanger
A
A
(f) Adequate fresh air through radiator
W
M
(g) Clean exterior of radiator
A
A
(h) Fan and alternator belt
M
Q
(i) Water pump(s)
W
Q
(j) Condition of flexible hoses and
connection
W
M
(k) Jacket water heater
W
M
(l) Inspect duct work, clean louvers
A
A
(m) Louver motors and controls
A
A
(a) Leakage
W
M
(b) Drain condensate trap
W
M
4. Exhaust System
© 2018 National Fire Protection Association
FIGURE A.8.3.1(b)
NFPA 110 (p. 1 of 3)
Sample Maintenance Log — Routine Maintenance, Operation, and Testing (RMOT).
2019 Edition
110-32
EMERGENCY AND STANDBY POWER SYSTEMS
EPSS Maintenance Log (continued)
Performed by
Service
Frequency
Component
Level 1
Level 2
(c) Insulation and fire hazards
Q
Q
(d) Excessive backpressure
A
A
(e) Exhaust system hangers and
supports
A
A
(f) Flexible exhaust section
S
S
W
M
Frequency
W — Weekly
M — Monthly
Q — Quarterly
S — Semiannually
A — Annually
Nos. indicate hours
Date
Fill in Appropriate Readings
5. Battery System
(a) Electrolyte level
(b) Terminals clean and tight
Q
Q
(c) Remove corrosion, case exterior
clean and dry
M
M
(d) Specific gravity or state of charge
M
M
(e) Charger and charge rate
M
M
(f) Equalize charge
M
M
(a) General inspection
W
M
(b) Tighten control and power wiring
connections
A
A
(c) Wire chafing where subject to
movement
Q
S
(d) Operation of safeties and alarms
S
S
(e) Boxes, panels, and cabinets
S
S
2 or M
2 or A
(g) Transfer switch main contacts
A
A
(h) Calibration of voltage-sensing
relays/devices
5 or A
5 or A
(i) Wire insulation breakdown
5/500
a
3/500b
W
M
6. Electrical System
(f) Circuit breakers, fuses
Note: Do not break manufacturer’s
seals or perform internal inspection
on these devices.
7. Prime Mover
(a) General inspection
(b) Service air cleaner
S
S
(c) Governor oil level and linkage
M
M
(d) Governor oil
A
A
(e) Ignition system — plugs, points, coil,
cap, rotor, secondary wire insulation
A
A
(f) Choke setting and carburetor
adjustment
S
S
(g) Injector pump and injectors for flow
rate pressure and/or spray pattern
A
A
(h) EPS at minimum of 30% nameplate
rating
3/4c
3/4c
© 2018 National Fire Protection Association
FIGURE A.8.3.1(b)
2019 Edition
Continued
NFPA 110 (p. 2 of 3)
ANNEX A
110-33
EPSS Maintenance Log (continued)
Performed by
Service
Frequency
Component
Level 1
Level 2
3/500
b
3/500
3/500
(j) Torque bolts
3/500
S — Semiannually
A — Annually
Nos. indicate hours
Date
b
(i) Valve clearance
Frequency
W — Weekly
M — Monthly
Q — Quarterly
Fill in Appropriate Readings
b
b
8. Generator
(a) Brush length, appearance, free to
move in holder
W
M
(b) Commutator and slip rings
S
S
(c) Rotor and stator
A
A
(d) Bearing(s)
A
A
(e) Bearing grease
A
A
(f) Exciter
A
A
(g) Voltage regulator
A
A
(h) Measure and record resistance
readings of windings with insulation
tester (Megger)
A
A
9. (a) General condition of EPSS, any
unusual condition of vibration,
leakage, noise, temperature, or
deterioration
W
M
(b) Service room or housing housekeeping
W
M
W
M
10. Restore system to automatic
operation condition
a Every 5 years or 500 hours
b Every 3 years or 500 hours
c Every 3 years for 4 hours
© 2018 National Fire Protection Association
FIGURE A.8.3.1(b)
NFPA 110 (p. 3 of 3)
Continued
In addition, load-add, load-shed, load demand control, load
optimization, and other operating and control features should
be tested at appropriate intervals. Logic controls that contain
load block information should be adjusted as necessary, and
load priorities should be reviewed as ATS loads change.
A.8.3.6 A battery load test should be performed quarterly.
A.8.4.1 Weekly inspection does not require running of the
EPS. Running unloaded generators as part of this weekly
inspection can result in long-term problems such as wet stack‐
ing. See Figure A.8.4.1(a) and Figure A.8.4.1(b).
A.8.4.2 Light loading creates a condition termed wet stacking,
indicating the presence of unburned fuel or carbon, or both,
in the exhaust system. Its presence is readily indicated by the
presence of continuous black smoke during engine-run opera‐
tion. The testing requirements of 8.4.2 are intended to reduce
the possibility of wet stacking. If equivalent loads are used for
exercising, it is suggested that all essential loads be energized
first, with the equivalent load used only to supplement the test.
If the normal power were to fail during the exercise period, it
would negate the urgency to automatically remove the equiva‐
lent load as described in 8.4.2.2.
The generator set manufacturer should be consulted where
the nameplate data do not indicate rating type. There is a
difference between prime and standby ratings. For example,
there are usually two kW nameplate ratings found on most
engine-driven generators: “standby” and “prime.” There can be
a significant difference between the resulting kW figures when
calculating 30 percent of nameplate — for example, a 100 kW
standby generator is normally considered an 80 kW set for
prime power: 100 kW × 30% = 30 kW, but 80 kW × 30% =
24 kW. A permanent record of the rating should be maintained
and readily available.
A.8.4.2.3 The generator set manufacturer should be consulted
where the nameplate data do not indicate rating type. There is
a difference between prime and standby ratings. For example,
there are usually two kW nameplate ratings found on most
engine-driven generators: “standby” and “prime.” There can be
2019 Edition
110-34
EMERGENCY AND STANDBY POWER SYSTEMS
EPSS Operation and Testing Log
Performed by
Date
Item*
Fill in Appropriate Readings
1. Maintenance schedule
2. RTM
3. Power fail
4. T/D start
5. Crank time
6. Transfer
7. (a) ac voltage
(b) Hz
(c) ac amperage
(d) ac kW
8. (a) Oil pressure
(b) dc amperage
9. (a) Oil pressure
(b) dc amperage
(c) W/A temp.
10. Restore normal
11. (a) Oil pressure
(b) dc amperage
(c) W/A temp.
(d) ac voltage
(e) Hz
(f) ac amperage
(g) ac kW
12. T/D retransfer
13. T/D stop
14. Auto mode
Comments
* See Suggested Operation and Testing Procedures for explanation of items.
© 2018 National Fire Protection Association
FIGURE A.8.4.1(a)
2019 Edition
Sample Operation and Testing Log for Rotating Equipment.
ANNEX B
110-35
Suggested Operation and Testing Procedures
Item*
Procedure
1.
Perform maintenance per Maintenance
Schedule
2.
Record running time meter (RTM) reading at
start and end of test.
3.
Simulate normal power failure from a “cold
start” by use of the test switch in automatic
transfer switch or by opening normal power
supply to EPSS.
4.
Observe and record time delay (T/D) on start.
5.
Record cranking time (terminates when engine
starts).
6.
Transfer load to EPS.
7.
Record ac voltage, frequency, amperage, kW.
Item*
Procedure
8.
Record initial oil pressure and battery-charging rate.
9.
Record oil pressure, battery-charging rate, and
water or air temperature after 15 minutes
running time.
10.
Return test switch to normal or reestablish
normal power supply at such time to cause a
minimum running time of 30 minutes under load.
11.
Record prime mover and ac instruments just
prior to transfer.
12.
Record time delay on retransfer.
13.
Record time delay on shutdown for units so
equipped.
14.
Place unit in automatic operation mode.
*See Operation and Testing Log.
FIGURE A.8.4.1(b)
Operation and Testing Procedures Suggested for Rotating Equipment.
a significant difference between the resulting kW figures when
calculating 30 percent of nameplate — for example, a 100 kW
standby generator is normally considered an 80 kW set for
prime power: 100 kW × 30% = 30 kW, but 80 kW × 30% =
24 kW. A permanent record of the rating should be maintained
and readily available.
A.8.4.3.1 The intent is to verify the starting function from
each ATS to the EPS by rotating the ATS that initiates the cold
engine start of the monthly test. For example, if the facility has
37 ATSs, it can take more than 3 years to verify the starting
function of the ATSs. Consideration should be given to ATS
criticality. Once the testing cycle is completed, in subsequent
years the testing order can be modified to reflect changes to
the EPSS.
tal load banks are not required. After the test, the fuel supply
should be replenished if necessary.
A.8.4.9.5.1 The generator set manufacturer should be consul‐
ted where the nameplate data do not indicate rating type.
There is a difference between prime and standby ratings. For
example, there are usually two kW nameplate ratings found on
most engine-driven generators: “standby” and “prime.” There
can be a significant difference between the resulting kW figures
when calculating 30 percent of nameplate — for example, a
100 kW standby generator is normally considered an 80 kW set
for prime power: 100 kW × 30% = 30 kW, but 80 kW × 30% =
24 kW. A permanent record of the rating should be maintained
and readily available.
Selected ATSs can be electrically operated at a different time
than the monthly operational test when required for opera‐
tional or safety considerations, provided the monthly require‐
ment of 8.4.6 is met.
A.8.4.9.7 The generator set manufacturer should be consulted
where the nameplate data do not indicate rating type. There is
a difference between prime and standby ratings. For example,
there are usually two kW nameplate ratings found on most
engine-driven generators: “standby” and “prime.” There can be
a significant difference between the resulting kW figures when
calculating 30 percent of nameplate — for example, a 100 kW
standby generator is normally considered an 80 kW set for
prime power: 100 kW × 30% = 30 kW, but 80 kW × 30% =
24 kW. A permanent record of the rating should be maintained
and readily available.
A.8.4.7 Circuit breakers should be tested under simulated
overload conditions every 2 years.
Annex B Diagrams of Typical Systems
A.8.4.6.1 This requirement is to simulate a power outage with‐
out turning off normal power. This requirement allows selected
ATSs to be transferred back to normal before the entire 30minute test is complete when required for operational or safety
considerations.
A.8.4.9 The intent of this requirement is to provide reasona‐
ble assurance that the EPSS with all of its auxiliary subsystems is
capable of running for the duration of its assigned class with its
running load. A full facility power outage is not intended for
this test but is recommended where a total facility power
outage has not occurred within the last 36 months. Supplemen‐
This annex is not a part of the requirements of this NFPA document
but is included for informational purposes only.
B.1 Typical Power Supply Systems. See Figure B.1(a) through
Figure B.1(e) for examples.
2019 Edition
110-36
EMERGENCY AND STANDBY POWER SYSTEMS
Full capacity primary
power sources
Alternate source
generator(s)
Main
OCD
Emergency
power supply (EPS)
Transformer
Non-EPSS
loads
Generator
Overcurrent device with
switching mechanism (OCD)
EPSS
Load 1
EPSS
Load 2
Automatic transfer switch
EPSS
Load 3
Automatic or manual
transfer device
Emergency power supply system (EPSS)
FIGURE B.1(a)
Typical Rotating Emergency Power Supply System.
Full capacity primary
power sources
Alternate source
generator units
Main OCD
Emergency power
supply (EPS)
EPSS distribution center (See Note 2)
Non-EPSS loads
Manual standard
or emergency
bypass switch
Level 1
Level 1 Level 1 or 2 EPSS load
EPSS load EPSS load EPSS load
Emergency power supply system (EPSS)
Transformer
Notes:
1. One alternate source generator unit of the paralleling
system to have sufficient capacity to carry all required
Level 1 loads.
Overcurrent device with
switching mechanism (OCD)
2. The EPSS distribution center can be installed in additional
cubicles as part of the paralleling board setup.
Automatic transfer switch
(Level 1 or 2)
FIGURE B.1(b)
2019 Edition
Typical Multiple-Unit Emergency Power Supply System.
Generator(s)
Automatic or manual
transfer device
Paralleling panel
Totalizing panel
ANNEX B
110-37
Full capacity primary
power sources
Alternate source
generators
Emergency power supply (EPS)
Non-EPSS
loads
EPSS
EPSS EPSS
loads EPSS loads loads
loads
Manual standard or
emergency bypass switch
For extended power outage protection,
reconnect to load side of automatic transfer switch.
Storage
battery
Bypass source
Emergency power supply system (EPSS)
Battery
charger
Transformer
Generator
Overcurrent device with
switching mechanism (OCD)
Automatic transfer switch
B2
dc load
B5
Automatic or manual
transfer device
Paralleling panel
B1
B3
B4
Inverter
monitor
Bypass
switch
Pos.
Line
Test
Auto.
Test
Inv.
Contacts B
12345
X
XX
X
XXX
XX X
X
Totalizing panel
FIGURE B.1(c)
Typical Composite Emergency Power Supply System.
2019 Edition
110-38
EMERGENCY AND STANDBY POWER SYSTEMS
Full capacity primary
power sources
Main OCD
Emergency power supply
system (EPSS)
Non-EPSS loads
Battery
charger
Storage
battery
Emergency power
supply (EPS)
To dc loads
Transformer
Overcurrent device with
switching mechanism (OCD)
FIGURE B.1(d)
2019 Edition
Typical Uninterruptible Power Supply (UPS) System.
ANNEX C
Utility
Utility
ATS
Generator
Generator
Y
Y
ATS
MECH
ATS
UPS
UPS
WC Chiller
Cooling
tower
PCWP
CWP
AHJ 2
Grac
panel
House
panel
UPS
AHJ 1
Grac
panel
House
panel
PCNP
AC Chiller
RC1
RC2
Rectifer
Rectifer
DC1
PDU
DC2
DC Conv
48VDC
OP1
48VDC
load
STS
RPP
Single
cord
DC Conv
48VDC
OP2
FIGURE B.1(e)
ATS
MECH
UPS
48VDC
panel1
110-39
PDU
PDU
Single
cord
RPP
48VDC
panel2
RPP
Typical
dual corded
server
Typical 911 Call Center in Designated Critical Operations Area.
Annex C Informational References
C.1 Referenced Publications. The documents or portions
thereof listed in this annex are referenced within the informa‐
tional sections of this standard and are not part of the require‐
ments of this document unless also listed in Chapter 2 for
other reasons.
C.1.1 NFPA Publications. National Fire Protection Associa‐
tion, 1 Batterymarch Park, Quincy, MA 02169-7471.
NFPA 20, Standard for the Installation of Stationary Pumps for
Fire Protection, 2019 edition.
NFPA 37, Standard for the Installation and Use of Stationary
Combustion Engines and Gas Turbines, 2018 edition.
NFPA 56, Standard for Fire and Explosion Prevention During
Cleaning and Purging of Flammable Gas Piping Systems, 2017
edition.
NFPA 58, Liquefied Petroleum Gas Code, 2017 edition.
NFPA 70®, National Electrical Code®, 2017 edition.
NFPA 70B, Recommended Practice for Electrical Equipment Main‐
tenance, 2016 edition.
NFPA 99, Health Care Facilities Code, 2018 edition.
NFPA 101®, Life Safety Code®, 2018 edition.
NFPA 111, Standard on Stored Electrical Energy Emergency and
Standby Power Systems, 2019 edition.
NFPA 54, National Fuel Gas Code, 2018 edition.
2019 Edition
110-40
EMERGENCY AND STANDBY POWER SYSTEMS
C.1.2 Other Publications.
C.1.2.1 ASCE Publications. American Society of Civil Engi‐
neers, 1801 Alexander Bell Drive, Reston, VA 20191.
ASCE/SEI 7, Minimum Design Loads for Buildings and Other
Structures, 2010.
C.1.2.2 ASTM Publications. ASTM International, 100 Barr
Harbor Drive, P.O. Box C700, West Conshohocken, PA
19428-2959.
ASTM D975, Standard Specification for Diesel Fuel Oils, 2015c.
ASTM D1835, Standard Specification for Liquefied Petroleum (LP)
Gases, 2013.
C.1.2.3 IEEE Publications. IEEE, Three Park Avenue, 17th
Floor, New York, NY 10016-5997.
NEMA MG 2, Safety Standard and Guide for Selection, Installa‐
tion and Use of Electric Motors and Generators, 2014.
C.1.2.5 NHC Publications. National Hurricane Center, 11691
SW 17th Street, Miami, FL 33165-2149.
SLOSH (Sea, Lake and Overland Surges from Hurricanes)
Model.
C.1.2.6 U.S. Government Publications. U.S. Government
Publishing Office, 732 North Capitol Street, NW, Washington,
DC 20401-0001.
FEMA 543, Design Guide for Improving Critical Facility Safety
from Flooding and High Winds, 2007.
FEMA 577, Design Guide for Improving Hospital Safety in Earth‐
quakes, Floods, and High Winds, 2007.
ANSI/IEEE 493, Recommended Practice for the Design of Reliable
Industrial and Commercial Power Systems, 2007.
C.2 Informational References. The following documents or
portions thereof are listed here as informational resources
only. They are not a part of the requirements of this document.
C.1.2.4 NEMA Publications. National Electrical Manufactur‐
ers Association, 1300 North 17th Street, Suite 900, Arlington,
VA 22209.
C.2.1 NFPA Publications. National Fire Protection Associa‐
tion, 1 Batterymarch Park, Quincy, MA 02169-7471.
ANSI/NEMA C 84.1, Standard for Electric Power Systems and
Equipment — Voltage Ratings (60 hertz), 2011.
NEMA MG 1, Standard for Motors and Generators, 2016.
2019 Edition
NFPA 72®, National Fire Alarm and Signaling Code®, 2019
edition.
C.3 References for Extracts in Informational Sections.
(Reserved)
INDEX
110-41
Index
Copyright © 2018 National Fire Protection Association. All Rights Reserved.
The copyright in this index is separate and distinct from the copyright in the document that it indexes. The licensing provi‐
sions set forth for the document are not applicable to this index. This index may not be reproduced in whole or in part by any
means without the express written permission of NFPA.
-AAdministration, Chap. 1
Application, 1.3
Equivalency, 1.4
Purpose, 1.2
Scope, 1.1
Approved
Definition, 3.2.1, A.3.2.1
Authority Having Jurisdiction (AHJ)
Definition, 3.2.2, A.3.2.2
Automatic Battery Charger, 5.6.4.6, A.5.6.4.6
Number of Batteries, 5.6.4.3, A.5.6.4.3
Otto or Diesel Cycle Prime Movers, 5.6.4.2, A.5.6.4.2
Size of Batteries, 5.6.4.4, A.5.6.4.4
Starting Systems, 5.6.4.1
Type of Battery, 5.6.4.5
Remote Controls and Alarms, 5.6.6, A.5.6.6
Emergency Power Supply System (EPSS)
Definition, 3.3.4, A.3.3.4
Explanatory Material, Annex A
-F-
-BBattery Certification
Definition, 3.3.1, A.3.3.1
Black Start
Definition, 3.3.2
-CClassification of Emergency Power Supply Systems
(EPSSs), Chap. 4
Class, 4.2, A.4.2
General, 4.1, A.4.1
Level, 4.4, A.4.4
Type, 4.3
-DDefinitions, Chap. 3
Diagrams of Typical Systems, Annex B
Typical Power Supply Systems, B.1
-EEmergency Power Supply (EPS)
Definition, 3.3.3, A.3.3.3
Emergency Power Supply (EPS): Energy Sources, Converters, and
Accessories, Chap. 5
Energy Converters — Capacity, 5.4, A.5.4
Energy Converters — Fuel Supply, 5.5
Energy Converters — General, 5.2
Energy Converters — Temperature Maintenance, 5.3
Energy Sources, 5.1
Rotating Equipment, 5.6
Control Functions, 5.6.5
General, 5.6.1
Generators, Exciters, and Voltage Regulators, 5.6.9
Miscellaneous Requirements, 5.6.10
Prime Mover Accessories, 5.6.3
Prime Mover Cooling Systems, 5.6.7
Prime Mover Exhaust Piping, 5.6.8
Prime Mover Ratings, 5.6.2
Prime Mover Starting Equipment, 5.6.4
Field Evaluation Body (FEB)
Definition, 3.3.5
Field Labeled (as applied to evaluated products)
Definition, 3.3.6
Fuel Tank
Day Fuel Tank
Definition, 3.3.7.1
Definition, 3.3.7
Enclosed Fuel Tank
Definition, 3.3.7.2
Integral Fuel Tank in EPS Systems
Definition, 3.3.7.3
Main Fuel Tank
Definition, 3.3.7.4
-IInformational References, Annex C
Installation and Environmental Considerations, Chap. 7
Distribution, 7.12
Exhaust System, 7.10
Fuel System, 7.9
General, 7.1
Heating, Cooling, and Ventilating, 7.7
Installation Acceptance, 7.13
Installed EPS Cooling System, 7.8
Lighting, 7.3
Location, 7.2
Indoor EPS Installations, 7.2.1
Outdoor EPS Installations, 7.2.2
Mounting, 7.4
Noise, 7.6, A.7.6
Protection, 7.11
Vibration, 7.5, A.7.5
-LLabeled
Definition, 3.2.3
2019 Edition
110-42
EMERGENCY AND STANDBY POWER SYSTEMS
Lamp
Definition, 3.3.8
Lead-Acid Battery
Definition, 3.3.9
Valve-Regulated (VRLA)
Definition, 3.3.9.1, A.3.3.9.1
Vented (Flooded)
Definition, 3.3.9.2, A.3.3.9.2
Listed
Definition, 3.2.4, A.3.2.4
-OOccupancy Category
Definition, 3.3.10
-QQualified Person
Definition, 3.3.11
-RReferenced Publications, Chap. 2
Routine Maintenance and Operational Testing, Chap. 8
General, 8.1, A.8.1
Maintenance and Operational Testing, 8.3
Manuals, Special Tools, and Spare Parts, 8.2, A.8.2
Operational Inspection and Testing, 8.4
Records, 8.5
-SShall
Definition, 3.2.5
Should
Definition, 3.2.6
Standard
Definition, 3.2.7
Switch
Automatic Transfer Switch (ATS)
Definition, 3.3.12.1
Bypass-Isolation Switch
Definition, 3.3.12.2
2019 Edition
Definition, 3.3.12
Nonautomatic Transfer Switch
Definition, 3.3.12.3
-TTransfer Switch Equipment, Chap. 6
ATS Features, 6.2
Engine Generator Exercising Timer, 6.2.11
General, 6.2.1, A.6.2.1
Indication of Transfer Switch Position, 6.2.13, A.6.2.13
Interlocking, 6.2.3, A.6.2.3
Isolation of Neutral Conductors, 6.2.15, A.6.2.15
Manual Operation, 6.2.4, A.6.2.4
Motor Load Transfer, 6.2.14
Nonautomatic Transfer Switch Features, 6.2.16, A.6.2.16
Indication of Transfer Switch Position, 6.2.16.2
Interlocking, 6.2.16.1
Source Monitoring, 6.2.2
Test Switch, 6.2.12
Time Delay at Engine Control Panel, 6.2.6
Time Delay Bypass If EPS Fails, 6.2.9
Time Delay on Engine Shutdown, 6.2.10
Time Delay on Retransfer to Primary Source, 6.2.8, A.6.2.8
Time Delay on Starting of EPS, 6.2.5, A.6.2.5
Time Delay on Transfer to EPS, 6.2.7
Time Delay at Engine Control Panel, 6.2.7.2
Time Delay Commencement, 6.2.7.1
Bypass-Isolation Switches, 6.4
Bypass-Isolation Switch Classification, 6.4.3, A.6.4.3
Bypass-Isolation Switch Rating, 6.4.2
Bypassing and Isolating Transfer Switches, 6.4.1
Operation, 6.4.4, A.6.4.4
Reconnection of Transfer Switch, 6.4.5
General, 6.1
Protection, 6.5
Accessibility, 6.5.4
General, 6.5.1, A.6.5.1
Overcurrent Protective Device Rating, 6.5.3, A.6.5.3
Short Circuit Current, 6.5.2
Requirements for Paralleled Generator Sets, 6.3
Sequence of Events for the Standards
Development Process
Committee Membership
Classifications1,2,3,4
Once the current edition is published, a Standard is opened for
Public Input.
The following classifications apply to Committee members
and represent their principal interest in the activity of the
Committee.
Step 1 – Input Stage
• Input accepted from the public or other committees for
consideration to develop the First Draft
• Technical Committee holds First Draft Meeting to revise
Standard (23 weeks); Technical Committee(s) with Correlating Committee (10 weeks)
• Technical Committee ballots on First Draft (12 weeks);
Technical Committee(s) with Correlating Committee
(11 weeks)
• Correlating Committee First Draft Meeting (9 weeks)
• Correlating Committee ballots on First Draft (5 weeks)
• First Draft Report posted on the document information
page
Step 2 – Comment Stage
• Public Comments accepted on First Draft (10 weeks) following posting of First Draft Report
• If Standard does not receive Public Comments and the
Technical Committee chooses not to hold a Second Draft
meeting, the Standard becomes a Consent Standard and
is sent directly to the Standards Council for issuance (see
Step 4) or
• Technical Committee holds Second Draft Meeting
(21 weeks); Technical Committee(s) with Correlating
Committee (7 weeks)
• Technical Committee ballots on Second Draft (11 weeks);
Technical Committee(s) with Correlating Committee
(10 weeks)
• Correlating Committee Second Draft Meeting (9 weeks)
• Correlating Committee ballots on Second Draft
(8 weeks)
• Second Draft Report posted on the document information page
Step 3 – NFPA Technical Meeting
• Notice of Intent to Make a Motion (NITMAM) accepted
(5 weeks) following the posting of Second Draft Report
• NITMAMs are reviewed and valid motions are certified
by the Motions Committee for presentation at the NFPA
Technical Meeting
• NFPA membership meets each June at the NFPA Technical Meeting to act on Standards with “Certified Amending Motions” (certified NITMAMs)
• Committee(s) vote on any successful amendments to the
Technical Committee Reports made by the NFPA membership at the NFPA Technical Meeting
1. M Manufacturer: A representative of a maker or marketer of a product, assembly, or system, or portion
thereof, that is affected by the standard.
2. U User: A representative of an entity that is subject to
the provisions of the standard or that voluntarily
uses the standard.
3. IM Installer/Maintainer: A representative of an entity that
is in the business of installing or maintaining a product, assembly, or system affected by the standard.
4. L Labor: A labor representative or employee concerned
with safety in the workplace.
5. RT Applied Research/Testing Laboratory: A representative
of an independent testing laboratory or independent applied research organization that promulgates
and/or enforces standards.
6. E Enforcing Authority: A representative of an agency or
an organization that promulgates and/or enforces
standards.
7. I Insurance: A representative of an insurance company,
broker, agent, bureau, or inspection agency.
8. C Consumer: A person who is or represents the ultimate
purchaser of a product, system, or service affected by
the standard, but who is not included in (2).
9. SE Special Expert: A person not representing (1) through
(8) and who has special expertise in the scope of the
standard or portion thereof.
NOTE 1: “Standard” connotes code, standard, recommended practice, or guide.
NOTE 2: A representative includes an employee.
NOTE 3: While these classifications will be used by the
Standards Council to achieve a balance for Technical Committees, the Standards Council may determine that new
classifications of member or unique interests need representation in order to foster the best possible Committee
deliberations on any project. In this connection, the Standards Council may make such appointments as it deems
appropriate in the public interest, such as the classification
of “Utilities” in the National Electrical Code Committee.
NOTE 4: Representatives of subsidiaries of any group are
generally considered to have the same classification as the
parent organization.
Step 4 – Council Appeals and Issuance of Standard
• Notification of intent to file an appeal to the Standards
Council on Technical Meeting action must be filed within
20 days of the NFPA Technical Meeting
• Standards Council decides, based on all evidence,
whether to issue the standard or to take other action
Notes:
1. Time periods are approximate; refer to published schedules for actual dates.
2. Annual revision cycle documents with certified amending motions take approximately 101 weeks to complete.
3. Fall revision cycle documents receiving certified amending motions take approximately 141 weeks to complete.
6/16-A
Submitting Public Input / Public Comment Through the Online Submission System
Soon after the current edition is published, a Standard is open for Public Input.
Before accessing the Online Submission System, you must first sign in at www.nfpa.org. Note: You will be asked to
sign-in or create a free online account with NFPA before using this system:
a. Click on Sign In at the upper right side of the page.
b. Under the Codes and Standards heading, click on the “List of NFPA Codes & Standards,” and then select
your document from the list or use one of the search features.
OR
a. Go directly to your specific document information page by typing the convenient shortcut link of
www.nfpa.org/document# (Example: NFPA 921 would be www.nfpa.org/921). Sign in at the upper right
side of the page.
To begin your Public Input, select the link “The next edition of this standard is now open for Public Input”
located on the About tab, Current & Prior Editions tab, and the Next Edition tab. Alternatively, the Next Edition
tab includes a link to Submit Public Input online.
At this point, the NFPA Standards Development Site will open showing details for the document you have
selected. This “Document Home” page site includes an explanatory introduction, information on the current
document phase and closing date, a left-hand navigation panel that includes useful links, a document Table of
Contents, and icons at the top you can click for Help when using the site. The Help icons and navigation panel
will be visible except when you are actually in the process of creating a Public Input.
Once the First Draft Report becomes available there is a Public Comment period during which anyone may
submit a Public Comment on the First Draft. Any objections or further related changes to the content of the First
Draft must be submitted at the Comment stage.
To submit a Public Comment you may access the online submission system utilizing the same steps as previously
explained for the submission of Public Input.
For further information on submitting public input and public comments, go to: http://www.nfpa.org/
publicinput.
Other Resources Available on the Document Information Pages
About tab: View general document and subject-related information.
Current & Prior Editions tab: Research current and previous edition information on a Standard.
Next Edition tab: Follow the committee’s progress in the processing of a Standard in its next revision cycle.
Technical Committee tab: View current committee member rosters or apply to a committee.
Technical Questions tab: For members and Public Sector Officials/AHJs to submit questions about codes and
standards to NFPA staff. Our Technical Questions Service provides a convenient way to receive timely and consistent technical assistance when you need to know more about NFPA codes and standards relevant to your work.
Responses are provided by NFPA staff on an informal basis.
Products & Training tab: List of NFPA’s publications and training available for purchase.
6/16-B
Information on the NFPA Standards Development Process
I. Applicable Regulations. The primary rules governing the processing of NFPA standards (codes, standards,
recommended practices, and guides) are the NFPA Regulations Governing the Development of NFPA Standards (Regs). Other
applicable rules include NFPA Bylaws, NFPA Technical Meeting Convention Rules, NFPA Guide for the Conduct of Participants in
the NFPA Standards Development Process, and the NFPA Regulations Governing Petitions to the Board of Directors from Decisions of
the Standards Council. Most of these rules and regulations are contained in the NFPA Standards Directory. For copies of the
Directory, contact Codes and Standards Administration at NFPA Headquarters; all these documents are also available on
the NFPA website at “www.nfpa.org.”
The following is general information on the NFPA process. All participants, however, should refer to the actual rules and
regulations for a full understanding of this process and for the criteria that govern participation.
II. Technical Committee Report. The Technical Committee Report is defined as “the Report of the responsible
Committee(s), in accordance with the Regulations, in preparation of a new or revised NFPA Standard.” The Technical
Committee Report is in two parts and consists of the First Draft Report and the Second Draft Report. (See Regs at
Section 1.4.)
III. Step 1: First Draft Report. The First Draft Report is defined as “Part one of the Technical Committee Report, which
documents the Input Stage.” The First Draft Report consists of the First Draft, Public Input, Committee Input, Committee
and Correlating Committee Statements, Correlating Notes, and Ballot Statements. (See Regs at 4.2.5.2 and Section 4.3.)
Any objection to an action in the First Draft Report must be raised through the filing of an appropriate Comment for
consideration in the Second Draft Report or the objection will be considered resolved. [See Regs at 4.3.1(b).]
IV. Step 2: Second Draft Report. The Second Draft Report is defined as “Part two of the Technical Committee Report,
which documents the Comment Stage.” The Second Draft Report consists of the Second Draft, Public Comments with
corresponding Committee Actions and Committee Statements, Correlating Notes and their respective Committee
Statements, Committee Comments, Correlating Revisions, and Ballot Statements. (See Regs at 4.2.5.2 and Section 4.4.)
The First Draft Report and the Second Draft Report together constitute the Technical Committee Report. Any outstanding
objection following the Second Draft Report must be raised through an appropriate Amending Motion at
the NFPA Technical Meeting or the objection will be considered resolved. [See Regs at 4.4.1(b).]
V. Step 3a: Action at NFPA Technical Meeting. Following the publication of the Second Draft Report, there is a period
during which those wishing to make proper Amending Motions on the Technical Committee Reports must signal their
intention by submitting a Notice of Intent to Make a Motion (NITMAM). (See Regs at 4.5.2.) Standards that receive
notice of proper Amending Motions (Certified Amending Motions) will be presented for action at the annual June NFPA
Technical Meeting. At the meeting, the NFPA membership can consider and act on these Certified Amending Motions as
well as Follow-up Amending Motions, that is, motions that become necessary as a result of a previous successful Amending
Motion. (See 4.5.3.2 through 4.5.3.6 and Table 1, Columns 1-3 of Regs for a summary of the available Amending Motions
and who may make them.) Any outstanding objection following action at an NFPA Technical Meeting (and any further
Technical Committee consideration following successful Amending Motions, see Regs at 4.5.3.7 through 4.6.5.3) must be
raised through an appeal to the Standards Council or it will be considered to be resolved.
VI. Step 3b: Documents Forwarded Directly to the Council. Where no NITMAM is received and certified in accordance
with the Technical Meeting Convention Rules, the standard is forwarded directly to the Standards Council for action on
issuance. Objections are deemed to be resolved for these documents. (See Regs at 4.5.2.5.)
VII. Step 4a: Council Appeals. Anyone can appeal to the Standards Council concerning procedural or substantive matters
related to the development, content, or issuance of any document of the NFPA or on matters within the purview of the
authority of the Council, as established by the Bylaws and as determined by the Board of Directors. Such appeals must be in
written form and filed with the Secretary of the Standards Council (see Regs at Section 1.6). Time constraints for filing an
appeal must be in accordance with 1.6.2 of the Regs. Objections are deemed to be resolved if not pursued at this level.
VIII. Step 4b: Document Issuance. The Standards Council is the issuer of all documents (see Article 8 of Bylaws). The
Council acts on the issuance of a document presented for action at an NFPA Technical Meeting within 75 days from the
date of the recommendation from the NFPA Technical Meeting, unless this period is extended by the Council (see Regs at
4.7.2). For documents forwarded directly to the Standards Council, the Council acts on the issuance of the document at its
next scheduled meeting, or at such other meeting as the Council may determine (see Regs at 4.5.2.5 and 4.7.4).
IX. Petitions to the Board of Directors. The Standards Council has been delegated the responsibility for the
administration of the codes and standards development process and the issuance of documents. However, where
extraordinary circumstances requiring the intervention of the Board of Directors exist, the Board of Directors may take
any action necessary to fulfill its obligations to preserve the integrity of the codes and standards development process
and to protect the interests of the NFPA. The rules for petitioning the Board of Directors can be found in the Regulations
Governing Petitions to the Board of Directors from Decisions of the Standards Council and in Section 1.7 of the Regs.
X. For More Information. The program for the NFPA Technical Meeting (as well as the NFPA website as information
becomes available) should be consulted for the date on which each report scheduled for consideration at the meeting will
be presented. To view the First Draft Report and Second Draft Report as well as information on NFPA rules and for up-todate information on schedules and deadlines for processing NFPA documents, check the NFPA website (www.nfpa.org/
docinfo) or contact NFPA Codes & Standards Administration at (617) 984-7246.
6/16-C
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